Patent Publication Number: US-2021187234-A1

Title: Headgear assembly with semi-rigid side arms

Description:
BACKGROUND 
     Field 
     The present disclosure relates to headgear assemblies for use in respiratory therapy. More particularly, certain aspects of the present disclosure relate to headgear assemblies including rigid side arms which are connected to the interface. 
     Description of Related Art 
     The treatment of respiratory ailments or conditions with therapies, such as NIV, Bi-level or CPAP, involves the delivery of pressurized air to the airways of a human via a conduit and a breathing apparatus (e.g., a mask or cannula). Typically, a mask creates at least a substantial “seal” on or around the nose and/or the mouth of a user while a cannula does not provide a seal but provides a delivery pathway for supplemental respiratory gas delivery. 
     A result of creating this “seal” is that the combination of the enclosure area of the breathing apparatus and its internal pressure creates a resulting force that attempts to push the breathing apparatus off of the face. To counteract this force, it is normal to use a headgear comprising a series of straps that pass around the back and/or top of a user&#39;s head. Headgear such as this are typically made from a compliant material, such as Breath-o-Prene™. The use of such a material results in the headgear having relatively little structure when not being worn. This lack of structure can give rise to the straps of the headgear becoming tangled, which in turn can make it difficult for a user to don the headgear and breathing apparatus. 
     The strap(s) require some form of adjustment to account for variation in head size, this adjustment mechanism is typically provided via an adjustment loop between the mask body and the head gear. The adjustment loop can have a hook-and-loop or similar fastener that permits an end of the strap to be passed through a mounting location on the mask or through a clip that attaches to the mask and then attached to another section of the strap. Such an arrangement permits adjustment of the headgear by positioning the end of the strap at a desired location on the other section of the strap to vary a size of the adjustment loop. 
     These types of mechanisms are one solution to providing an adjustment mechanism for the headgear and, thus, the interface assembly. Such systems also require a reasonable level of user interaction and, as a result, is prone to misuse or mis-adjustment (e.g., over-tightening). As a practical matter, micro-adjustment of such systems is difficult and time-consuming to accomplish. The creation of practical and not so practical solutions to this has been the subject of considerable development effort from a number of organizations, which has resulted in numerous patents. 
     Further, these traditional headgear are usually configured to have some elasticity. This can result in the headgear stretching over, and applying pinching forces to, the user&#39;s head, which can be uncomfortable. It is desirable to make headgear and breathing apparatus that are easy to use and comfortable to wear because this may improve a user&#39;s compliance with the therapy being provided. 
     SUMMARY 
     The systems and devices described herein have innovative aspects, no single one of which is indispensable or solely responsible for their desirable attributes. Without limiting the scope of the claims, some of the advantageous features will now be summarized. 
     In some embodiments, a headgear assembly is provided. The headgear assembly includes a pair of opposing, semi-rigid side arms, each side arm configured to be pivotally coupled to an interface at a single location, each side arm configured to extend from the single location across the user&#39;s cheeks and above the user&#39;s ears in use. The headgear assembly includes a top strap coupled to the pair of opposing, semi-rigid side arms, the top strap configured to extend over the top of a user&#39;s head. The headgear assembly includes a rear strap coupled to the pair of opposing, semi-rigid side arms, the rear strap configured to extend around the rear of a user&#39;s head. The headgear assembly includes a chin strap coupled to the pair of opposing, semi-rigid side arms, the chin strap configured to extend below the user&#39;s chin. 
     The headgear assembly includes an adjustment mechanism configured to allow movement between a semi-rigid side arm and the interface. In some embodiments, the adjustment mechanism includes a pair of components that are telescopically engaged. The headgear assembly includes the interface. In some embodiments, an upper portion of the pair of opposing, semi-rigid side arms is bifurcated. In some embodiments, the upper portion includes a top strap connection point configured to couple to the top strap. In some embodiments, the upper portion includes a rear strap connection point configured to couple to the rear strap. In some embodiments, a lower portion of the pair of opposing, semi-rigid side arms is bifurcated. In some embodiments, the lower portion includes a chin strap connection point configured to couple to the chin strap. In some embodiments, an upper portion of the pair of opposing, semi-rigid side arms is bifurcated and a lower portion of the pair of opposing, semi-rigid side arms is bifurcated. The headgear assembly includes a connecting member extending between the interface and a semi-rigid side arm. In some embodiments, the top strap and rear strap are arranged to form a bifurcated upper end of the headgear assembly and the chin strap and the connecting member form a bifurcated lower end of the headgear assembly. In some embodiments, the connecting member includes a twist such that the connecting member extends between an angled plane and a vertical plane. In some embodiments, the connecting member includes a male component of an adjustment mechanism. In some embodiments, the connecting member includes a bend. In some embodiments, the pair of opposing, semi-rigid side arms comprises an upper portion extending from an interface to a location above the user&#39;s ear and a lower portion having a first end that connects to the upper portion and a second end that connects to the interface below the connection of the upper portion. In some embodiments, the chin strap is configured to be a chin strap or a rear neck strap. 
     In some embodiments, a headgear assembly is provided. The headgear assembly includes a pair of side arms. Each side arm includes a translational adjustment mechanism configured to allow translational adjustment of the side arm. Each side arm includes a rotating adjustment mechanism configured to allow rotational adjustment of the side arm relative to an interface. In some embodiments, the rotating adjustment mechanism is vertically above the translational adjustment mechanism in use. In some embodiments, the rotating adjustment mechanism and the translational adjustment mechanism comprise a bend. 
     In some embodiments, a headgear assembly is provided. The headgear assembly includes a pair of side arms. Each side arm includes a first rotational adjustment mechanism configured to allow rotational adjustment of the side arm relative to an interface. Each side arm includes a second rotational adjustment mechanism configured to allow rotational adjustment between a lower member and an upper member of the side arm, wherein the first and second rotational adjustment mechanisms are spaced apart along the side arm. 
     In some embodiments, a headgear assembly is provided. The headgear assembly includes a pair of side arms. The headgear assembly includes a top strap, a rear strap, a first chin strap, and a second chin strap. In some embodiments, the first and second chin straps are spaced apart from each other and extend between the pair of side arms in use. 
     In some embodiments, a semi-rigid side arm for a side portion of a headgear assembly of a patient interface is provided. The semi-rigid side arm includes an elongate body extending between a first end and a second end. The semi-rigid side arm includes a first projection and a second projection projecting from the body at the first end. The semi-rigid side arm includes a third projection and a fourth projection projecting from the body at the second end. In some embodiments, each of the projections having a connection portion for connecting to straps of the headgear assembly or to the patient interface. In some embodiments, the elongate body and each of the projections have a thickness between 0.5 mm and 3 mm. In some embodiments, the elongate body extends along a longitudinal axis and wherein, the first and second projections project from the elongate body at different angles to each other and the third and fourth projections project from the elongate body at different angles to each other. In some embodiments, the first and third projections project away from the elongate body in substantially opposed directions, and the second and fourth projections project away from the elongate body in substantially opposed directions. 
     In some embodiments, an interface assembly for use in respiratory therapy is provided. The interface assembly includes an interface and a headgear assembly. In some embodiments, each side of the headgear assembly includes an upper portion connected to the interface and adapted to extend from the interface to a location above a user&#39;s ear. In some embodiments, each side of the headgear assembly includes a lower portion having a first end that connects to the upper portion and a second end that connects to the interface below the connection of the upper portion to the interface. In some embodiments, the connection location of at least one of the ends of the lower portion is adjustable. In some embodiments, the connection location of at least one of the ends of the lower portion is discretely adjustable. 
     All of these embodiments are intended to be within the scope of the disclosure herein. These and other embodiments will become readily apparent to those skilled in the art from the following detailed description having reference to the attached figures, the disclosure not being limited to any particular disclosed embodiment(s). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features, aspects, and advantages of the present disclosure are described with reference to the drawings of certain embodiments, which are intended to schematically illustrate certain embodiments and not to limit the disclosure. 
         FIG. 1  illustrates a perspective view of a full face headgear assembly and full face interface. 
         FIG. 2A  illustrates a perspective view of a user, a headgear assembly, and an interface. 
         FIG. 2B  illustrates a side view of the user, the headgear assembly, and the interface of  FIG. 2A . 
         FIG. 3  illustrates a side view of the user, the headgear assembly, and the interface of  FIG. 2A . 
         FIG. 4A  illustrates a side view of a side arm of the headgear assembly of  FIG. 2A . 
         FIG. 4B  illustrates a side view of various angles of the side arm of the headgear assembly of  FIG. 2A . 
         FIG. 4C  illustrates a side view of various angles of the side arm of the headgear assembly of  FIG. 2A . 
         FIG. 5A  illustrates a side view of a female component of an adjustment mechanism of the headgear assembly of  FIG. 2A . 
         FIG. 5B  illustrates a side view of a male component of the adjustment mechanism of the headgear assembly and the interface of  FIG. 2A . 
         FIG. 6A  illustrates a top view of a retracted configuration of the adjustment mechanism of the headgear assembly and the interface of  FIG. 2A . 
         FIG. 6B  illustrates a top view of an extended configuration of the adjustment mechanism of the headgear assembly and the interface of  FIG. 2A . 
         FIG. 7A  illustrates a side view of a pivot connection of the headgear assembly and the interface of  FIG. 2A . 
         FIG. 7B  illustrates a front view of the pivot connection of the headgear assembly and the interface of  FIG. 2A . 
         FIG. 7C  illustrates a top view of the pivot connection of the headgear assembly and the interface of  FIG. 2A . 
         FIG. 8  illustrates a chin strap of the headgear assembly of  FIG. 2A . 
         FIG. 9  illustrates a side view of a user, a headgear assembly, and an interface. 
         FIG. 10A  illustrates a side view of the user, the headgear assembly, and the interface of  FIG. 9 . 
         FIG. 10B  illustrates a side view of the user and the headgear assembly of  FIG. 9  and an interface. 
         FIG. 11  illustrates a side view of a user, a headgear assembly, and an interface. 
         FIG. 12  illustrates a side view of the user and the headgear assembly of  FIG. 11 . 
         FIG. 13  illustrates a side view of an adjustment mechanism of the headgear assembly and the interface of  FIG. 11 . 
         FIG. 14A  illustrates a side view of a user, a headgear assembly, and a full-face under-nose interface. 
         FIG. 14B  illustrates a side view of the user, the headgear assembly of  FIG. 14A , and a full-face over-nose interface. 
         FIG. 15  illustrates a side view of an adjustment mechanism of the headgear assembly and the interface of  FIG. 14A . 
         FIG. 16A  illustrates a front side view of an adjustment mechanism of the headgear assembly of  FIG. 14A . 
         FIG. 16B  illustrates a back side view of the adjustment mechanism of the headgear assembly of  FIG. 14A . 
         FIG. 16C  illustrates a cross-sectional view of the adjustment mechanism of the headgear assembly of  FIG. 14A  along line C-C in  FIG. 16B . 
         FIG. 17A  illustrates a side view of a user, a headgear assembly, and an interface. 
         FIG. 17B  illustrates a side perspective view of the headgear assembly and the interface of  FIG. 17A . 
         FIG. 18  illustrates a side view of a user, a headgear assembly, and an interface. 
         FIG. 19A  illustrates a side view of a user, a headgear assembly, and an interface in a first chin strap configuration, and  FIG. 19B  illustrates a side view of the user, the headgear assembly, and the interface of  FIG. 19A  in a second chin strap configuration. 
         FIG. 20  illustrates a perspective view of a user, a headgear assembly, and an interface, and  FIG. 21  illustrates a side view of the user and the headgear assembly of  FIG. 20 . 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of systems, components and methods of assembly and manufacture will now be described with reference to the accompanying figures, wherein like numerals refer to like or similar elements throughout. Although several embodiments, examples and illustrations are disclosed below, it will be understood by those of ordinary skill in the art that the inventions described herein extends beyond the specifically disclosed embodiments, examples and illustrations, and can include other uses of the inventions and obvious modifications and equivalents thereof. The terminology used in the description presented herein is not intended to be interpreted in any limited or restrictive manner simply because it is being used in conjunction with a detailed description of certain specific embodiments of the inventions. In addition, embodiments of the inventions can comprise several novel features and no single feature is solely responsible for its desirable attributes or is essential to practicing the inventions herein described. 
     Certain terminology may be used in the following description for the purpose of reference only, and thus are not intended to be limiting. For example, terms such as “above” and “below” may refer to directions in the drawings to which reference is made. Terms such as “front,” “back,” “left,” “right,” “rear,” and “side” describe the orientation and/or location of portions of the components or elements within a consistent but arbitrary frame of reference which is made clear by reference to the text and the associated drawings describing the components or elements under discussion. The terms “horizontal” and “vertical” are used relative to the interface or headgear assembly properly positioned on a user with the user&#39;s head in an upright orientation unless otherwise noted or made clear by the context of the disclosure. The term “horizontal” can refer to a line which is parallel or substantially parallel to the sagittal axis. The term “horizontal” can refer to a line which is parallel or substantially parallel to the anteroposterior axis (dorsoventral). The term “horizontal” can refer to a direction which is perpendicular to the coronal or frontal plane. The term “vertical” can refer to a line which is parallel or substantially parallel to the longitudinal axis. The term “vertical” can refer to a line which is parallel or substantially parallel to the craniocaudal axis. The term “vertical” can refer to a line which is perpendicular to the transverse plane. Moreover, terms such as “first,” “second,” “third,” and so on may be used to describe separate components. Such terminology may include the words specifically mentioned above, derivatives thereof, and words of similar import. 
     As used herein the term “semi-rigid” shall refer to the ability of a headgear or material to resist stretching relative to the loads to which it may be subjected. Thus, a component such as a side arm may be semi-rigid in one or more directions and may be less rigid in one or more other directions. In some configurations, the side arm is configured to be substantially rigid in a width or vertical direction, in use. In some configurations, the side arm is configured to be substantially rigid in a lengthwise, longitudinal or horizontal direction, in use. In some configurations, the side arm is configured to be less rigid in a third direction, such as a thickness direction or toward and away from the cheeks of the user, in use. The third direction can be along the left-right axis (frontal axis). This flexibility in one direction allows the headgear assemblies to conform to a user&#39;s head while providing rigidity in a direction that stabilizes and minimizes dislodging of the interface on a user&#39;s face. A semi-rigid side arm, for example, can resist stretching that would loosen or stretch one or more straps during use and/or shift the placement of the respiratory interface relative to the user. 
       FIG. 1  illustrates an example of a full-face headgear assembly and full-face interface. Full-face headgear assemblies typically require upper and lower headgear connection points to provide the sufficient retention forces in the appropriate directions. The upper and lower headgear connection points are required in order to achieve an effective seal between the full-face interface and a user&#39;s face. Typically, the headgear assembly requires four points of adjustment or connection to the full-face interface as shown in  FIG. 1 . 
     The full-face headgear assembly and full-face interface is configured to provide a supply of pressurized breathable gases to a patient&#39;s airway. The full-face headgear assembly  14  is connected to a frame  12 . The frame  12  is part of the interface and comprises a substantially triangular component having two lower headgear connections  16  (forming the lower points of the triangle) and a forehead support  18  (forming the upper point of the triangle). The forehead support  18  comprises an elongate member that in use extends upwardly, away from the headgear connections  16 , towards the patient&#39;s forehead. The headgear assembly  14  also comprises one more headgear straps that are configured to extend around and retains the interface  10  on the patient&#39;s head, in use. 
     The interface can include a sealing cushion comprising an integrally formed seal housing and flexible cushion. The frame  12  further comprises a sealing cushion connection to couple to the sealing cushion  10 . The seal housing is configured to provide a substantially rigid breathing chamber about the patient&#39;s nose and/or mouth. In the embodiment shown in  FIG. 1 , the sealing housing is configured to attach to the sealing cushion connection of the frame  12 . The flexible cushion is configured to engage a patient&#39;s face such that a substantially airtight seal is formed about the patient&#39;s nose, mouth or nose and mouth. The flexible cushion can be made from silicone, thermoplastic elastomer or any other appropriate material capable of at least partially conforming to the facial geometry of the patient. In the embodiment shown in  FIG. 1 , the flexible cushion comprises a rolling bridge located proximal to the patient&#39;s nasal bridge, in use. The rolling bridge is configured to allow an upper portion of the flexible cushion to roll during hinging movement of the upper portion relative to a lower portion of the flexible cushion. The interface is configured to seal around the nose and mouth. In some embodiments, the interface seals only around or under the user&#39;s nose. In some embodiments, the interface seals only around or in the user&#39;s mouth. 
     Typically, full-face headgear assemblies are cumbersome and complicated, due in part to the plurality of straps, connection points, and adjustable parts. These headgear assemblies are typically difficult to put on (don) and take off (doff). As one example, the headgear assembly shown in  FIG. 1  includes lower side straps that are positioned below a user&#39;s ears in use. The lower side straps either have to be disconnected during fitting of the full-face interface or the lower side straps have to be pulled over the user&#39;s ears which can cause discomfort. 
     As shown in  FIG. 1 , forehead supports or T-pieces are common in full-face headgear assemblies. The forehead support can make the full-face headgear assembly intrusive and claustrophobic for users. However, there are tradeoffs with removing the forehead support. Without the forehead support, the full-face interface has a tendency to ride up the user&#39;s face. The headgear assembly preferably therefore provides force vectors that counteract this movement if the forehead support is removed. 
     In addition, these headgear assemblies have a steep learning curve to master, including the ability to tighten and adjust each strap. Adjustment mechanisms require user interaction and, as a result, are prone to misuse or maladjustments including over-tightening. In some cases, adjustment of the headgear assembly can be difficult and time-consuming. As disclosed herein, there is an opportunity to simplify headgear assemblies and improve the ease of use. 
       FIG. 2A  illustrates an interface  10  and a headgear assembly  100  including semi-rigid side arms  102  that are pivotally connected to the full-face interface  10 , as described herein. The headgear assembly  100  can be used with any interface  10  including an under-nose full-face interface and over-nose full-face interface.  FIG. 2B  illustrates a side view of  FIG. 2A . 
     The headgear assembly  100  includes a pair of opposing, semi-rigid side arms  102 . In use, the semi-rigid side arms  102  are placed such that one side arm  102  is on each side of the head of the user. The headgear assembly  100  includes an adjustment mechanism  104  that provides adjustability between the headgear assembly  100  and the interface  10 . The adjustment mechanism  104  can adjust the distance between the side arm  102  and the interface  10  a distance “D” as shown in  FIG. 3 . The headgear assembly  100  includes connecting members  108  that provide the pivotal connection. Each side arm  102  couples to a connecting member  108  which couples to the interface  10 . 
     The headgear assembly  100  can include one or more straps. The headgear assembly  100  includes a chin strap  110  that extends under the user&#39;s chin in use. The headgear assembly  100  includes a top strap  112  that extends over the top or crown of a user&#39;s head in use. The headgear assembly  100  includes a rear strap  114  that extends around the rear of a user&#39;s head in use. 
       FIG. 4A  illustrates the side arm  102 . The side arm  102  includes an upper end  116  and a lower end  118 . The upper end  116  is bifurcated to form a top strap connection point  120  and a rear strap connection point  122 . The top strap connection point  120  and the rear strap connection point  122  form an angle there between. The angle can be approximately 90 degrees (e.g., 70 degrees, 80 degrees, 90 degrees, 100 degrees, 110 degrees, etc.). The top strap connection point  120  is substantially vertical and the rear strap connection point  122  is substantially horizontal. The side arm  102  includes an ear arch  124 . The ear arch  124  passes above the ear of the user in use. The side arm  102  includes a mid-section  126  between the upper end  116  and the lower end  118 . The side arm  102  includes a cheek curve  128 . The cheek curve  128  passes near the cheekbone of the user in use. The cheek curve  128  is concave. The cheek curve  128  is concave toward the eyes of the user. The cheek curve  128  provides a smooth curve between the mid-section  126  and the lower end  118  of the side arm  102 . The cheek curve  128  slopes downward toward the lower end  118 . 
     The lower end  118  is bifurcated to form a chin strap connection point  130  and a support  132 . The chin strap connection point  130  and the support  132  form an angle there between. The angle can be approximately 90 degrees (e.g., 70 degrees, 80 degrees, 90 degrees, 100 degrees, 110 degrees, etc.). The chin strap connection point  130  is substantially vertical and the support  132  is substantially horizontal. The support  132  couples to the adjustment mechanism  104 , or a component thereof. The adjustment mechanism  104  includes a female component  138 , as described herein. The side arm  102  includes a pull tab  140  and a fastener  142 , as described herein.  FIG. 4A  illustrates the side arm  102  designed to be adjacent to the right side of the user&#39;s face during use. The side arm  102  designed to be adjacent to the left side of the user&#39;s face during use can include any or all of the features shown in  FIG. 4A  and can be a mirror image of the illustrated side arm  102 .  FIGS. 4B and 4C  illustrate the side arm adjacent to the left side of the user&#39;s face. 
     As described herein the upper end  116  and the lower end  118  are bifurcated. The side arm  102  includes an elongate body extending between the upper end  116  and the lower  118 . While upper and lower are used herein, the upper end  116  and the lower end  118  can be a first end and a second end. The upper end  116  includes a first projection and a second projection which project from the body at the upper end  116 . The first projection includes the top strap connection point  120 . The second projection includes rear strap connection point  122 . The lower end  118  includes a third projection and a fourth projection which project from the body at the lower end  118 . The third projection includes the chin strap connection point  130 . The fourth projection includes the support  132 . Other configurations of the projections are contemplated. Each of the first, second and third projections have a connection portion for connecting the straps of the headgear assembly  100  to the side arm  102 . The fourth projection has a connection portion, in the form of the support  132 , for connecting the interface  10  to the side arm  102  (via the adjustment mechanism). 
     In some embodiment, the elongate body of the side arm  102  is thin. The side arm  102  has a constant thickness. In some embodiments, the side arm  102  does not have a constant thickness. The side arm  102  has a thickness between 0.5 mm and 3 mm. The upper end  116  of the side arm  102  has a constant thickness. In some embodiments, the upper end  116  does not have a constant thickness. The upper end  116  of the side arm  102  has a thickness between 0.5 mm and 3 mm. The lower end  118  of the side arm  102  has a constant thickness. In some embodiments, the lower end  118  does not have a constant thickness. The lower end  118  of the side arm  102  has a thickness between 0.5 mm and 3 mm. Each of the projections has a thickness of 0.5 mm and 3 mm. Examples of thicknesses used herein include 0.5 mm, 0.75 mm, 1 mm, 1.25 mm, 1.5 mm, 1.75 mm, 2 mm, 2.25 mm, 2.5 mm. 2.75 mm, and 3 mm, including any range of two or more thicknesses. Other thicknesses are contemplated for the side arm  102 , or portions thereof, including 0.25 mm, 3.25 mm, 3.5 mm, 3.75 mm, 4 mm, 4.25 mm, 4.5 mm, 4.75 mm, 5 mm, 5.25 mm, 5.5 mm. 5.75, and 6 mm, including any range of two or more thicknesses. The thickness of the side arm  102  can increase between 0.5 mm and 2 mm if the side arms  102  are intra-moulded. This increase in thickness accounts for the textile thickness. In some embodiments, there is a layer of padding applied to an internal surface of the side arms  102 . In some embodiments, the padding is foam, but other materials are contemplated. The thickness of the side arm  102  increases between 0.5 mm and 4 mm if the side arm  102  includes padding. The padding has a thickness between 0.5 mm and 4 mm. Examples of thicknesses of the padding include 0.5 mm, 0.75 mm, 1 mm, 1.25 mm, 1.5 mm, 1.75 mm, 2 mm, 2.25 mm, 2.5 mm. 2.75 mm, 3 mm, 3.25 mm, 3.5 mm, 3.75 mm, and 4 mm including any range of two or more thicknesses. Other thicknesses of the padding are contemplated. 
     The features of the side arm have substantially constant thickness. The elongate body of the side arm  102  has constant thickness. In some embodiment, the elongate body of the side arm  102  has variable thickness. The upper end  116  of the side arm  102  has constant thickness. In some embodiment, the upper end  116  of the side arm  102  has variable thickness. The lower end  118  of the side arm  102  has constant thickness. In some embodiment, the lower end  118  of the side arm  102  has variable thickness. In some embodiments, the elongate body of the side arm  102  is planar when not in use, but the elongate body of the side arm  102  is curved to match the user&#39;s face during use. In use, the lower ends  118  of the headgear assembly  100  curve inwardly toward each other. In some embodiments, the elongate body of the side arm  102  is not planar. In some embodiments, the upper end  116  of the side arm  102  is planar. In some embodiments, the upper end  116  is not planar. In some embodiments, the lower end  118  of the side arm  102  is planar. In some embodiments, the lower end  118  is not planar. In some embodiments, one or more projections including the connection point is planar. In some embodiments, one or more projections including the connection point is not planar. In some embodiments, each projection is planar. 
     The elongate body of the side arm  102  extends along a longitudinal axis. The first and second projections project from the elongate body at different angles to each other. The first and second projections project from the elongate body at different angles relative to the longitudinal axis. The third and fourth projections project from the elongate body at different angles to each other. The third and fourth projections project from the elongate body at different angles relative to the longitudinal axis. In some embodiments, the first and second projections project from the elongate body at the same angle to each other. 
       FIG. 4B  illustrates various angles of the side arm  102 . The side arm  102  includes a longitudinal axis. The side arm  102  includes angle A. The angle A is the angle between the upper end  116  and the longitudinal axis. The angle A is the angle between the second projection and the longitudinal axis. The angle A is the angle between the rear strap connection point  122  and the longitudinal axis. The angle A is 110 degrees. The angle A is between 80 degrees and 150 degrees. Examples of angles include 80 degrees, 90 degrees, 100 degrees, 110 degrees, 120 degrees, 130 degrees, 140 degrees, and 150 degrees, including any range of two or more angles. Other examples of angles for angle A include 50 degrees, 60 degrees 70 degrees, 160 degrees, 170 degrees, and 180 degrees, including any range of two or more angles. 
     The side arm  102  includes angle B. The angle B is the angle between the lower end  118  and the longitudinal axis. The angle B is the angle between the fourth projection and the longitudinal axis. The angle B is the angle between the support  132  and the longitudinal axis. The angle B is 120 degrees. The angle B is between 90 degrees and 140 degrees. Examples of angles include 90 degrees, 100 degrees, 110 degrees, 120 degrees, 130 degrees, and 140 degrees, including any range of two or more angles. Other examples of angles for angle B include 50 degrees, 60 degrees 70 degrees, 80 degrees, 150 degrees, 160 degrees, 170 degrees, and 180 degrees, including any range of two or more angles. 
       FIG. 4C  illustrates various angles of the side arm  102 . The angle C is the angle between the first projection and the second projection. The angle C is the angle between the top strap connection point  120  and the rear strap connection point  122 . The angle C is 90 degrees. The angle C is between 80 degrees and 120 degrees. Examples of angles for angle C include 80 degrees, 90 degrees, 100 degrees, 110 degrees, and 120 degrees, including any range of two or more angles. Other examples of angles for angle C include 50 degrees, 60 degrees, 70 degrees, 130 degrees, 140 degrees, 150 degrees, 160 degrees, 170 degrees, and 180 degrees, including any range of two or more angles. 
     The angle D is the angle between the third projection and the forth projection. The angle D is the angle between the chin strap connection point  130  and the support  132 . The angle D is 90 degrees. The angle D is between 80 degrees and 120 degrees. Examples of angles for angle D include 80 degrees, 90 degrees, 100 degrees, 110 degrees, and 120 degrees, including any range of two or more angles. Other examples of angles for angle D include 50 degrees, 60 degrees, 70 degrees, 130 degrees, 140 degrees, 150 degrees, 160 degrees, 170 degrees, and 180 degrees, including any range of two or more angles. 
     The angle E is the angle between the first projection and the third projection. The angle E is the angle between top strap connection point  120  and the chin strap connection point  130 . The angle E is 20 degrees. The angle E is between 0 degrees and 40 degrees. Examples of angles for angle E include 0 degrees, 10 degrees, 20 degrees, 30 degrees, and 40 degrees, including any range of two or more angles. Other examples of angles for angle E include 50 degrees, 60 degrees, 70 degrees, 80 degrees, 90 degrees, 100 degrees, 110 degrees, 120 degrees, and 130 degrees, including any range of two or more angles. The first and third projections project away from the elongate body in substantially opposed directions. 
     The angle F is the angle between the second projection and the fourth projection. The angle F is the angle between rear strap connection point  122  and the support  132 . The angle F is 20 degrees. The angle F is between 0 degrees and 40 degrees. Examples of angles for angle F include 0 degrees, 10 degrees, 20 degrees, 30 degrees, and 40 degrees, including any range of two or more angles. Other examples of angles for angle F include 50 degrees, 60 degrees, 70 degrees, 80 degrees, 90 degrees, 100 degrees, 110 degrees, 120 degrees, and 130 degrees, including any range of two or more angles. The second and fourth projections project away from the elongate body in substantially opposed directions. 
     The side arms  102  are configured to extend between the interface  10 , across a user&#39;s cheeks to a point above the user&#39;s ears where the top strap  112  and the rear strap  114  are connected thereto. The side arms  102  are semi-rigid and planar. The side arms  102  are able to flex in a direction that is into the page of  FIG. 4 , or towards the user&#39;s cheeks, in use. The side arms  102  resist bending in a vertical direction and/or a horizontal direction in use. The side arms  102  are made from a plastic material. In some embodiments, the side arms  102  are not made from a plastic material. 
     The semi-rigid material of the side arms  102  provides structure to the headgear assembly  100 . The side arms  102  transfer forces to the top strap  112  and the rear strap  114 . The side arms  102  resist rotation of the interface  10  on the user&#39;s face. The side arms  102  enable a single connection point between the headgear assembly  100  and each side of the interface  10 . The side arms  102  transfer and direct forces from the interface  10  to the top strap  112  and the rear strap  114  of the headgear assembly  100 . 
     As described herein, the upper end  116  of the side arm  102  is bifurcated to provide connection points for the top strap  112  and the rear strap  114 . The upper end  116  includes the top strap connection point  120  that directs the top strap  112  toward a respective direction (e.g., around the crown of the user&#39;s head). The upper end  116  includes the rear strap connection point  122  that directs the rear strap  114  toward a respective direction (e.g., around the back of the user&#39;s head). The top strap connection point  120  and rear strap connection point  122  include apertures through which the top strap  112  and the rear strap  114  can pass. The side arm  102  is curved to form the ear arch  124  that is designed to sit above a user&#39;s ear in use. The ear arch  124  avoids contact with top of user&#39;s ears to avoid discomfort. 
     With reference to the orientation of  FIG. 4 , the side arm  102  curves downwards in a left to right direction to pass between a user&#39;s temple and the user&#39;s ear. The side arm  102  curves downward in a left to right direction to pass across their cheeks to the lower end  118 . The side arm  102  includes the cheek curve  128 . The lower end  118  extends at an angle from the mid-section  126  of the side arm  102  so that the lower end  118  extends across the user&#39;s cheek in use. The lower end  118  can be positioned horizontal in use when the user is upright. The lower end  118  is closer to horizontal in comparison to the mid-section  126 . If not exactly horizontal, then the lower end  118  can be angled slightly upward as shown in  FIG. 4  or angled slightly downward, depending on user facial and/or cranial geometry. The horizontal or substantially horizontal lower end  118  helps to counteract blow-off forces that act in a direction that is perpendicular to the user&#39;s face. The lower end  118  includes the chin strap connection point  130 . The chin strap connection point  130  includes an aperture through which a lateral end of the chin strap  110  can pass. 
       FIGS. 5A and 5B  illustrate components of the adjustment mechanism  104 .  FIG. 5A  illustrates a portion of the side arm  102 . The side arm  102  couples to the adjustment mechanism  104 . The support  132  includes a forward portion of the lower end  118  of the side arm  102 . The support  132  couples to the female component  138  of the adjustment mechanism  104 . The pull tab  140  couples to the female component  138  at a fixed end  144 . The pull tab  140  includes the fastener  142  near a free end  146  of the pull tab  140 . 
       FIG. 5B  illustrates additional components of the adjustment mechanism  104 . The adjustment mechanism  104  includes a male component  148 . The male component  148  is designed to slide within the female component  138  to provide an adjustment between the headgear assembly  100  and the interface  10 . 
     Some embodiments disclosed herein involve a headgear assembly  100  that upon fitment to the head of a user automatically adjusts to the correct size and, once in use, transforms in properties from an elasticated “stretchy” strap/strapping to an “inelastic” strap/strapping. In some configurations, the headgear assembly  100  (alone or as integrated in an interface assembly  10 ,  100 ) exhibits a relatively small contraction force that tends to shorten the headgear assembly  100 . When coupled to an interface  10 , the headgear assembly  100  and interface  10  cooperate to define a perimeter of the interface assembly  10 ,  100 , which is reduced in length as a result of the contraction force toward a minimum perimeter length. Although not likely to be perfectly circular, the perimeter length is often referred to as a “circumference.” Thus, with such an arrangement, the interface assembly  10 ,  100  can be positioned on the user&#39;s head and will automatically contract to or very near a proper head size, in a manner similar to an elasticated or “stretchy” headgear. The contraction or retraction force preferably is sufficient to support the weight of the interface assembly  10 ,  100  and at least substantially keep the interface assembly  10 ,  100  in place on the user&#39;s head at the smallest head size or minimum useful perimeter length of the interface assembly  10 ,  100 , which may or may not coincide with the minimum perimeter length. In some configurations, the contraction force can be between about 0.5 Newtons and about 5.2 Newtons, or between about 1 Newton and about 2.6 Newtons, or between about 1 Newton and about 1.5 Newtons, including any value and sub-range within these ranges. In other configurations, the contraction force may be insufficient to support the weight of the interface and may require manual assistance to move the interface to a sealed position on the user&#39;s face. However, preferably, once the headgear assembly  100  is sufficiently contracted, it is then held in place by, for example, directional lock(s). In some configurations, the contraction force is only sufficient or is configured to support the weight of the headgear assembly  100 . 
     However, in at least some configurations, the contraction force is less than is necessary to maintain the interface  10  in sealed contact with the user&#39;s face during treatment/use. That is, the contraction force, alone, cannot resist the blow-off force. In some configurations, the contraction force is insufficient to resist the blow-off force throughout a range of usable perimeter lengths or headgear sizes. Therefore, the headgear assembly  100  and/or interface assembly  10 ,  100  also exhibits an inelastic behavior in response to forces tending to elongate the headgear assembly  100  or increase the perimeter length of the interface assembly  10 ,  100 . The headgear assembly  100  and/or interface assembly  10 ,  100  can have a locked mode that can produce a locking force tending to resist expansion, elongation or lengthening of the perimeter length. The locking force can be sufficient to resist elongation, or at least any significant elongation, of the perimeter length in response to blow-off forces. In some configurations, the locking force is sufficient to resist elongation in response to the highest blow-off forces expected with a variety of uses or treatments (e.g., Bi-Level or CPAP, NIV, etc.). In some configurations, the locking force may be selected for one or more particular uses/therapies, but may not be suitable for all uses/therapies. In some configurations, the locking force may be selected to resist elongation in response to forces in addition to blow-off forces, such as hose pull forces, for example. 
     In some configurations, the headgear assembly  100  and/or interface assembly  10 ,  100  also exhibits a yield force, above which expansion or elongation of the perimeter length is permitted. Preferably, the yield force is greater than the expected blow-off force. In some configurations, the yield force is greater than the expected blow-off force and the hose pull force. Thus, such a headgear assembly  100  and/or interface assembly  10 ,  100  has a reserve. Preferably, the yield force is set low enough that a user can at least relatively conveniently apply an elongation force to the headgear assembly  100  and/or interface assembly  10 ,  100  sufficient to exceed the yield force in order to permit the interface assembly  10 ,  100  to lengthen and to be applied to the user&#39;s head. As described above, the contraction force reduces the perimeter length toward a proper head size. 
     In some configurations, the headgear assembly  100  and/or interface assembly  10 ,  100  automatically transitions between a contraction mode, a locked mode and a yield mode in response to the presence or absence of external forces. For example, the headgear assembly  100  and/or interface assembly  10 ,  100  moves toward or to the minimum perimeter length in the absence of external lengthening or expanding forces. A lengthening or expansion force that is greater than the yield force can be applied to increase the perimeter length of the headgear assembly  100  and/or interface assembly  10 ,  100  to a length sufficient to permit the interface assembly  10 ,  100  to be positioned on the user&#39;s head. Once the lengthening or expansion force is removed (or reduced to below the contraction force), the contraction force acts to automatically reduce the perimeter length to or substantially to the proper head size such that the interface assembly  10 ,  100  is supported on the user&#39;s head. Upon the start of treatment (application of blow-off force) and/or application of hose pull force, the headgear assembly  100  and/or interface assembly  10 ,  100  automatically transforms to the locked mode to resist elongation, or at least resist any significant elongation, or increase of the perimeter length. At the end of treatment, or at any time as desired, a force above the yield force can be applied to the headgear assembly  100  and/or interface assembly  10 ,  100  to increase the perimeter length and permit removal of the interface assembly  10 ,  100  from the user&#39;s head. 
     Advantageously, with such an arrangement, micro-adjustments of the perimeter length of the headgear assembly  100  and/or interface assembly  10 ,  100  can be accomplished quickly and conveniently. For example, during treatment or use, the interface  10  can be manipulated to effect micro-adjustment of the perimeter length. For instance, in the event of a leak between the interface  10  and the user&#39;s face, the interface  10  can be wiggled or otherwise moved to effect a micro-adjustment of the perimeter length to address the leak. In some cases, the seal of the interface  10  may be compressed against the user&#39;s face, which can allow the contraction force to automatically reduce the perimeter length. Upon release of the interface  10 , the headgear assembly  100  and/or interface assembly  10 ,  100  locks at, or very near, the reduced perimeter length. Thus, such configurations permit the headgear assembly and/or interface assembly  10 ,  100  to micro-adjust, or move to an adjusted perimeter length, as a result of small manipulations (e.g., wiggling) of the interface  10 . Manipulation of other portions of the interface assembly  10 ,  100  (e.g., headgear assembly  100  or breathing tube/gases conduit) can similarly result in micro-adjustment. Because of the nature of the human head and/or the conditions under which interface assemblies  10 ,  100  are used, quick and convenient micro-adjustment can dramatically improve performance and user satisfaction of an interface assembly  10 ,  100 . Treatment often occurs at night and/or under other situations when the user is lying down. Thus, the headgear assembly  100  can be in contact with surface, such as a pillow or bed. Movement of the user&#39;s head relative to such surfaces can cause movement of the headgear assembly  100 , which can alter the fit of the headgear assembly  100 . For example, hair can move or “compress” beneath the headgear assembly  100 , which can alter the fit. The headgear straps may move up, down or rotationally on the head, which can alter the fit. Such alterations in fit can result in leaks between the interface  10  and the user&#39;s face. The above-described adjustment technology can permit such changes in fit to be addressed automatically or with small manipulations of the interface  10  or other portions of the interface assembly  10 ,  100 . Moreover, the interface assembly  10 ,  100  can be removed and reapplied and automatically adjust to at or very near a proper headgear size. In contrast, if conventional non-stretch headgear is moved from its desired adjustment position, such as by mistake or as a result of cleaning, it can be difficult and time-consuming to re-establish the desired adjustment position. Conventional elasticated headgear addresses the adjustment issue, but because the contraction force must resist the highest expected blow-off and hose pull forces at the smallest useable headgear size, elasticated headgear applies a relatively large pressure to the user&#39;s head that is only partially relieved by the application of blow-off force. Such pressure may be substantial for a user with a relatively large head size and low treatment pressure. 
     The connecting member  108  provides the connection between the headgear assembly  100  and the interface  10 . The connecting member  108  includes or is formed as a single piece with the male component  148  of the adjustment mechanism  104 . The connecting member  108  includes a front end  150  and a rear end  152 . The male component  148  is located near the rear end  152  of the connecting member  108 . The connecting member  108  includes a rotational adjustment mechanism or pivot connection  156 . The pivot connection  156  is located near the front end  150  of the connecting member  108 . 
     In use, the male component  148  is inserted into the female component  138  of the adjustment mechanism  104 . The male component  148  is inserted into the female component  138  in a telescoping manner. In some methods of use, the interface  10  slides toward the face of the user as the male component  148  slides further within the female component  138 . The connecting member  108  includes a pull tab loop  154 . The pull tab  140  couples to the female component  138  as shown in  FIG. 5A . The free end  146  of the pull tab  140  is passed through the pull tab loop  154 . The user can pull the free end  146  to move the headgear assembly and the interface  10  toward each other. The pull tab  140  is designed to pass through and around the pull tab loop  154  such that the fastener  142  can be secured upon sufficient tightening of the adjustment mechanism  104 . The pull tab  140  limits or prevents further extension movement of the adjustment mechanism  104  once the fastener  142  is secured. 
       FIG. 6A  illustrates a top view of a retracted configuration of the adjustment mechanism  104 .  FIG. 6B  illustrates a top view of an extended configuration of the adjustment mechanism  104 . The distance “D” is illustrated as a measurement between the pivot connection  156  and a location (e.g., the front edge) on the female component  138 . In the retracted configuration, the side arm  102  is closer to the interface  10 . In the extended configuration, the side arm  102  is farther from the interface  10 . 
       FIGS. 6A and 6B  illustrate the connecting member  108  including the pull tab loop  154  and the pivot connection  156 , the female component  138  and the male component  148  of the adjustment mechanism  104 , and the pull tab  140 . In both the retracted configuration and the extended configuration, the pull tab  140  secures the side arm  102  to the connecting member  108  to maintain the configuration. In the retracted configuration, the male component  148  is mostly or completely housed within the female component  138  and the interface  10  is close to the user&#39;s face and/or headgear assembly  100 . In an extended configuration, the male component  148  partially protrudes from the front end of the female component  138  so that the interface  10  is spaced away from the user&#39;s face and/or headgear assembly  100 . In the retracted configuration there is more overlap between the female component  138  and the male component  148  relative to the extended configuration. 
     The adjustment mechanism  104  is configured to adjustably position the interface  10  relative to the headgear assembly  100  by adjusting a distance “D” between the pivot connection  156  and the side arm  102 . The adjustment mechanism  104  includes the male component  148  coupled to or formed with the connecting member  108 . The connecting member  108  is located at a front end of the male component  148  or, as described above, can be unitarily formed with the male component  148 . The male component  148  is slideably engaged with or received by the female component  138  at a rear end. The male component  148  or connecting member  108  also includes the pull tab loop  154  that protrudes from an outer surface adjacent the pivot connection  156  at the front end. The pull tab loop  154  is configured to receive the free end  146  of the pull tab  140  as shown in  FIGS. 6A and 6B . 
     The adjustment mechanism  104  includes the female component  138 , which is coupled to or formed with the side arm  102 . The female component  138  comprises a housing that is configured to receive the male component  148  in a sliding or telescopic manner. The female component  138  has a rectangular housing. In some embodiments, the female component has any shaped housing. The housing of the female component  138  has any cross-sectional shape (e.g., round, circular, elliptical, polygonal, triangular, etc.). The female component  138  is attached to the support  132  of the side arm  102 . The female component  138  is integrally formed with the side arm  102 . In some embodiments, the female component  138  is not integrally formed with the side arm  102 . The pull tab  140  is connected to an outer surface of or another suitable location on the female component  138 . The pull tab  140  comprises an elongate piece of flexible material. In some embodiments, the pull tab  140  is made of non-flexible material. The pull tab  140  includes the fixed end  144  attached to the rear end of the female component  138  and the opposing, free end  146 . The free end  146  includes the fastener configured to secure the adjustment mechanism  140 . The fastener  142  is a hook component of a hook and loop fastener that is configured to secure the free end  146  of the pull tab  140  to another part of the pull tab  140 , which forms the loop component of the hook and loop fastener. In some embodiments, the fastener  142  is any other type of fastener. The pull tab  140  can limit further movement of the male component  148  relative to the female component  138 . 
     The pull tab  140  is configured to pass through the pull tab loop  154 , be folded back over onto itself, and fastened into place by the fastener  142 . In some methods of use, the user pulls on the free ends  146  of the pull tabs  140  either rearward towards the user&#39;s face, in use, or laterally away from the user&#39;s face. Pulling the free ends  146  of the pull tabs  140  will cause the male component  148  to be pulled towards the female component  138 , thus increasing the overlap between the male component  148  and the female component  138 . The male component  148  telescopes within the female component  138 . Pulling the free ends  146  of the pull tabs  140  will tighten the fit of the interface  10  with the user&#39;s face. The user can secure the fastener  142  once the desired fit is achieved. To loosen the fit of the interface  10 , the fastener  142  can be released and the interface  10  pulled away from the user&#39;s face. The spring force within the compressed seal of the interface  10  may cause the interface  10  to be pushed away from the user&#39;s face when the fastener  142  is released. The pull tab  140  is made from Breathoprene™ or another suitable textile and foam laminate. In some embodiments, the pull tab  140  is made from any other suitable material. The pull tab  140  is preferably non-stretch. In some embodiments, the pull tab  140  has some elasticity. 
     The male component  148  and the female component  138  comprise different materials. In some embodiments, the male component  148  and the female component  138  comprise the same material. The male component  148  and the female component  138  comprise materials that reduce friction and binding between the male component  148  and the female component  138 . The male component  148  and the female component  138  of the adjustment mechanism  104  are substantially rigid and straight in order to enable linear sliding and minimize binding during adjustment. The male component  148  and the female component  138  are horizontal in use. The male component  148  and the female component  138  provide adjustment in the direction of blow-off forces. 
     The male component  148  and the female component  138  of the adjustment mechanism  104  provide rigidity between the side arm  102  and the interface  10 . The use of a rigid or semi-rigid adjustment mechanism  104  can be beneficial in applications in which the force vectors between the pressurized interface seal and the headgear assembly are not aligned. This misalignment in force vectors results in a situation where moments are generated, which can be at least partially counteracted through the rigidity within the headgear assembly  100 . The forces are counteracted by the selection of the torsional rigidity and bending rigidity characteristics of adjustment mechanism  104 , and/or other components of the headgear assembly  100 , such as the side arms  102  and the straps  110 ,  112 ,  114 , the combination of which significantly increases the level of rotational stability for the headgear assembly  100  and interface  10 . In some embodiments, the adjustment mechanism  104  is semi-rigid in one or more directions and less rigid in one or more other directions. In some configurations, the adjustment mechanism  104  is configured to be substantially rigid in a width or vertical direction, in use. In some configurations, the adjustment mechanism  104  is configured to be substantially rigid in a lengthwise, longitudinal or horizontal direction, in use. In some configurations, the adjustment mechanism  104  is configured to be less rigid in a third direction, such as a thickness direction or toward and away from the cheeks of the user, in use. This flexibility in one direction allows the adjustment mechanism  104  to conform to a user&#39;s head while providing rigidity in a direction that stabilizes and minimizes dislodging of the interface on a user&#39;s face. 
       FIGS. 7A-7C  illustrate the pivot connection  156  between the interface  10  and the headgear assembly  100 . The interface  10  includes lateral sides. The lateral sides form a generally triangular shape of the interface  10 , such that the lateral sides are skewed relative to a vertical plane. As described herein, the connecting member  108  includes the pivot connection  156 . The pivot connection provides a pivotal or rotational movement of the connecting member  108 , and therefore the headgear assembly  100 , relative to the interface  10 . The connecting member  108  is designed to lie flat against the lateral sides of the interface  10 . 
     The pivot connection  156  is provided between a front end of the connecting member  108  and the upper lateral sides of the interface  10 . The pivot connection  156  includes a pivot axis  164 . The pivot connection  156  pivots about a pivot axis  164  and allows the angle of the interface  10  relative to the side arms  102  to be adjusted as per the arrow in  FIG. 7A . The pivot axes  164  are centrally located on the lateral sides of the housing of the interface  10 , as shown in  FIGS. 7B and 7C . The pivot axes  164  are located above the air inlet  168 . In some embodiments, the pivot axes  164  are located below the air inlet  168 . 
     The pivot connection  156  has a high level of friction between the connecting member  108  and the interface  10  to allow the angle of the connecting member  108  to be selectively changed by a user but to prevent unintentional angular adjustment when the interface  10  is in use. A high friction washer (e.g., made from an elastomer) is positioned between the pivot connection  156  of the connecting member  108  and the interface  10 . Other embodiments to provide friction between the connecting member  108  and the interface  10  are contemplated. In some embodiments, the pivot connection  156  has a low level of friction between the connecting member  108  and the interface  10 . 
     The connecting member  108  can include a transition  158 . The transition  158  is located between the pivot connection  156  and the male component  148 . The transition  158  includes an upper edge  160  and a lower edge  162 . The connecting member  108  includes the transition  158  which twists to change the plane that the male component  148  of the adjustment mechanism  104  lies in. The upper edge  160  is twisted outwards relative to the lower edge  162 , so that the male component  148  and pull tab loop  154  lie along a substantially vertical plane. The twist is shown in  FIG. 7B  which shows the transition between the skewed plane of the pivot connection  156  and the vertical plane of the male component  148  and the pull tab loop  154 . The connecting member  108  includes a vertical plane  166  near the pull tab loop  154 . The pivot axis  164  is skewed relative to the vertical plane  166 . The transition  158  provides a planar connection between the male component  148  and the female component  138  to enable free movement there between. The transition  158  enables the lower ends  118  of the side arms  102  to be aligned with the user&#39;s cheeks so that the side arms  102  sit flush against the cheeks and the edges of the side arms  102  do not dig in. 
       FIG. 8  illustrates an embodiment of a strap which includes two lateral ends  172  and a middle portion  174  there between. The chin strap  110 , the top strap  112 , and the rear strap  114  can have any or all of the following features of the strap shown in  FIG. 8 . 
     The lateral end  172  is sized to be passed through the aperture of the corresponding strap connection point of the side arm  102 . The lateral ends  172  have a width W 1  that is narrower than a width W 2  of the middle portion  174 . The narrower lateral ends  172  are configured to pass through apertures in the side arms  102  and double back on themselves. The wider middle portion  174  acts as an end stop to prevent over tightening of the strap. The middle portion  174  is sized not to pass through the apertures in the side arms  102 . The middle portion  174  can be enlarged to provide increased stability and comfort on the user&#39;s head. Each lateral end  172  can include a fastener  176 . The fastener  176  can be a component (e.g., hook component) of a hook and loop fastener such that the fastener  176  is configured to pass through and around the corresponding aperture on the side arm  102 . The fastener  176  can be secured to another part of the strap, which acts as the other component, to secure the headgear assembly  100  in a configuration that fits the user&#39;s head. The fastener  176  can be secured after the headgear assembly  100  is positioned to provide an effective seal between the user&#39;s face and the interface  10 . 
     The chin strap  110 , the top strap  112 , and the rear strap  114  are made from any suitable material. The chin strap  110 , the top strap  112 , and/or the rear strap  114  are made from foam and textile laminate material (e.g. Breathoprene™). The top strap  112  is inelastic. In some embodiments, the top strap  112  is elastic. The chin strap  110  is elastic. In some embodiments, the chin strap  110  is inelastic. The rear strap  114  is elastic. In some embodiments, the rear strap  114  is inelastic. Other combinations of elastic and inelastic straps are contemplated. 
       FIGS. 1-8  illustrate various embodiments of components of headgear assembly  100 . The features of any embodiment described herein can be combined with any other embodiment described herein. Any of the following features can be included separately or in combination with components described herein. The adjustment mechanism  104  is integrally formed with the side arm  102 . In some embodiments, the adjustment mechanism  104  is not integrally formed with the side arm  102 . The female component  138  can be integrally formed with the support  132  of the side arm  102 . 
     Each of the side arms  102  is intra-moulded as described herein. In some embodiments, the side arms  102  are not intra-moulded.  FIGS. 11-13  provide examples of intra-moulded side arms. The side arm  102  includes a textile casing that completely surrounds a core. The textile casing is a tube or other enclosed shaped. The core comprises a plastic material which provides strength to the textile casing. As described herein, one or more additional components can be formed by the same process, such as the top strap, the rear strap and/or the chin strap. In some intra-moulding processes, a molten plastic is injected onto a textile material or into a preformed textile casing. The intra-moulded side arm  102  includes a cover layer partially or completely surrounding a core. The cover layer can be constructed from a soft fabric, textile, foam or similar cushioning materials on at least an internal surface of the side arm  102 . The core may be formed by injection moulding a semi-rigid plastic into a cavity or hollow center of the cover layer. The intra-moulded side arms  102  include a textile or foam covering on at least an internal surface. 
     Other or alternative configurations are contemplated. In some embodiments, the adjustment mechanism  104  is omitted. In some embodiments, the side arms  102  could be permanently and/or rigidly connected to the interface  10 . In some embodiments, the components have different shapes. In some embodiments, the connecting member  108  can extend further laterally from the sides of the interface  10 . This arrangement would reduce contact between the side arms  102  and the user&#39;s cheeks which may improve comfort. 
     In some embodiments, the adjustment mechanism  104  is in the reverse arrangement than the configuration shown in  FIGS. 1-8 . The side arm  102  includes the male component  148 . The connecting member  108  includes the female component  138 . The male component  148  couples or is formed with the support  132  of the side arm  102 . The support arm  102  and/or the male component  148  include the pull tab loop  154 . The side arms  102  can form the male component  148  and/or the pull tab loop  154 . The female component  138  couples or is formed with the connecting member  108 . The pull tab  140  couples to the female component  138 . In this configuration, the user pulls the pull tab  140  toward the interface  10  to adjust to adjust the distance of the adjustment mechanism  104 . 
     The adjustment mechanism  104  allows for continuous sliding or telescoping positions, as per the embodiment of  FIGS. 1-8 . In some embodiments, the adjustment mechanism  104  allows for discrete adjustment. In some embodiments, the adjustment mechanism  104  includes a ratchet for incremental adjustment. The male component  148  can include gears or teeth. The female component  138  can include a pawl. The distance that the adjustment mechanism  104  can travel is determined by the size of the gears or teeth. 
     The straps can include any configuration or shape. One or more straps are adjustable by the user by adjusting the fasteners  176  connected to the lateral ends  172 . In some embodiments, the rear strap  114  is not adjustable. The rear strap  114  has a fixed length. In some embodiments, the top strap  112  is not adjustable. The top strap  112  has a fixed length. The chin strap  110 , top strap  112 , and the rear strap  114  can be any combination of elastic or inelastic. The chin strap  110  can be elastic or inelastic. The top strap  112  can be elastic or inelastic. The rear strap  112  can be elastic or inelastic. Two or more straps can be elastic. Two or more straps can be inelastic. The top strap  112  can have a fit and forget arrangement. In the fit and forget arrangement, the top strap  112  is adjusted once by the user to fit around the crown of the head. In subsequent uses, the user does not have to remove or adjust the top strap  112 . The rear strap  114  can have a fit and forget arrangement. In some embodiment, rear strap  114  is adjusted once by the user to fit around the back of the head. In subsequent uses, the user does not have to remove or adjust the rear strap  114 . Instead the user can apply the headgear assembly  100  using a similar method as a baseball cap by placing the top strap  112  and/or the rear strap  114  against the head and bringing the interface  10  toward the face. Examples of fit and forget arrangements are included in  FIGS. 11 and 12 . The top strap  112  is intra-moulded as described herein. The rear strap  114  is intra-moulded as described herein. In some embodiments, the top strap  112  is integrally formed with the side arms  102 . In some embodiments, the rear strap  114  is integrally formed with the side arms  102 . 
     The pivot connection  156  can have any configuration or shape. In some embodiments, the pivot connection  156  has discrete positions. In some embodiments, the pivot connection  156  allows for infinite rotational positions. In some embodiments, the pivot connection  156  includes a ratchet style adjustment. In some embodiments, the pivot connection  156  is low friction to allow the interface  10  to self-adjust to various angles on the user&#39;s face. In some embodiments, the pivot connection  156  is high friction to maintain the position of the pivot connection  156 . In some embodiments, the pivot connection  156  is provided by a malleable metal joint. 
     The headgear assembly  100  is used in conjunction with an interface that seals around the nose and mouth. In some embodiments, the headgear assembly  100  is used in conjunction with an interface that seals around the nose. In some embodiments, the headgear assembly  100  is used in conjunction with an interface that seals around the mouth. In some embodiments, the headgear assembly  100  is used in conjunction with an interface that seals under the nose. 
       FIG. 9  illustrates an interface  20  and a headgear assembly  200  including semi-rigid side arms  202 , as described herein. The headgear assembly  200  can be substantially the same as the headgear assembly  100  except as described below. Thus, any features not specifically described can be substantially the same as or similar to corresponding features of the headgear assembly  100  or other headgear assemblies described herein, or can be of another suitable arrangement. The headgear assembly  200  can include any features of the headgear assemblies described herein. The headgear assembly  200  can include a chin strap  210 , a top strap  212 , and a rear strap  214 . 
     The headgear assembly  200  can be used with any interface including those described herein.  FIG. 10A  illustrates a side view of the headgear assembly  200  of  FIG. 9 . The headgear assembly  200  is used in combination with an interface  20  that seals around a user&#39;s mouth and on the lower surfaces of the user&#39;s nose. The interface  20  can seal on the lateral lower sides or flanks of the user&#39;s nose. The seal exposes the tip of the user&#39;s nose. The interface  20  does not seal on the bridge of the user&#39;s nose.  FIG. 10B  illustrates a side view of the headgear assembly  200 . The headgear assembly  200  is used in combination with the interface  10  which is an over-the-nose full-face interface that is configured to seal on or near the bridge of the user&#39;s nose. 
     The headgear assembly  200  can include a pair of opposing semi-rigid side arms  202 . Each side arm  202  is designed to be positioned on one side of head of the user. While only one side arm  202  is shown in  FIG. 10A , the other side arm  202  can have the same or similar features and can be a mirror image of the illustrated side arm  202 . The headgear assembly  200  can include a connecting member  208  that connects the side arms  202  to the interface  20 . 
     The side arm  202  includes an upper end  216  and a lower end  218 . The upper end  216  is bifurcated and forms a top strap connection point  220  and a rear strap connection point  222 . The side arm  202  includes an ear arch  224 . The ear arch  224  passes above the ear of the user in use. The side arm  202  includes a mid-section  226  between the upper end  216  and the lower end  218 . The side arm  102  includes a cheek curve  228 . The cheek curve  228  passes near the cheekbone of the user in use. 
     The lower end  218  is bifurcated and forms a chin strap connection point  230  and an extension  234 . The extension  234  extends toward or to the interface  20 . The extension  234  includes a pivot connection  256 . The lower ends of the side arms  202  are permanently coupled to the interface  20  via the pivot connection  256 . The lower ends of the side arms  202  are not intended for consumer removal from the interface  20 . The lower ends of the side arms  202  form a pivot connection  256  with the interface  20 . The headgear assembly  200  does not include an adjustment mechanism as described in  FIGS. 2A-8 . 
     The extension  234  of the side arms  202  includes two segments  278 ,  280 . The two segments  278 ,  280  form an elbow, bend, or dog-leg. The segment  278  is horizontal or substantially horizontal in use. The segment  280  bends or extends upwards towards the pivot connection  256  from the segment  278 . This two segment construction allows a force vector to be applied to the interface  20  closer to the chin region. This two segment construction counteracts blow-off forces and minimizes leaks in this area. The construction also allows the interface  20  to pivot at a location close to the center of the interface  20  which allows the amount of engagement between the interface  20  and the user&#39;s nose to be adjustable. The interface  10  can be pivoted such that the upper half of the interface  10  is rotated towards the user&#39;s nose thus increasing engagement with the nose. The interface  10  can be pivoted such that the upper half of the interface  10  is rotated away from the nose. The interface  10  can be pivoted until the preferred fit is achieved. 
       FIG. 11  illustrates an interface  10  and a headgear assembly  300  including integrally formed side arms  302  and a top strap  312 . The headgear assembly  300  can be substantially the same as the headgear assembly  100  except as described below. Thus, any features not specifically described can be substantially the same as or similar to corresponding features of the headgear assembly  100  or other headgear assemblies described herein, or can be of another suitable arrangement. The headgear assembly  300  can include any features of the headgear assemblies described herein. While only one side arm  302  is shown in  FIGS. 11-13 , the other side arm  302  can have the same or similar features and can be the same or similar to of the illustrated side arm  302 . As described herein, the side arms  302  are integrally formed with the top strap  312 . The male and female components of the top strap  312  are connected to the respective side arm  302 . In the illustrated embodiment, the side arm  302  on the user&#39;s right side is connected to the female component of the top strap  312  and the side arm  302  on the user&#39;s left side is connected to the male component of the top strap  312 , but the reverse configuration is contemplated. The headgear assembly  300  can include the chin strap  310  and the rear strap  314 . The side arm  302  includes a rear strap connection point  322 . The side arm  302  includes a chin strap connection point  330 . The headgear assembly includes the adjustment mechanism  304  and the pivot connection  356 . The rear strap  314  is adjustable. In some embodiments, the rear strap  314  is not adjustable. The chin strap  310  is adjustable. In some embodiments, the chin strap  310  is not adjustable. The chin strap  310  has a single width over the length of the chin strap  310 . In some embodiments, the chin strap  310  has two or more widths over the length of the chin strap  310 .  FIG. 12  shows the upper end of the headgear assembly  300  and  FIG. 13  shows the lower end of the headgear assembly  300 . 
     The headgear assembly  300  includes the integrally formed side arms  302  and top strap  312 . The side arms  320  and the top strap  312  are integrally formed as a single component. The side arms  302  and/or the top strap  312  can include a textile covering. The textile covering covers at least a portion of the side arms  302  and/or the top strap  312 . In some embodiments, the textile covering covers the side arms  302  and/or the top strap  312  in their entirety. The side arms  302  and/or the top strap  312  are intra-moulded. In some methods of manufacturing of the side arms  302 , molten plastic is injected into one or more textile tubes. The plastic and the textile tubes form a unitary structure. The side arms  302  and the top strap  312  can be separately formed and later joined at a connector  306 . The connector is formed during an over-molding process, but could be formed during the intra-moulding process. 
     The top strap  312  includes an adjustment mechanism  382  that allows for incremental adjustment of the top strap  312 . The adjustment mechanism  382  is located at a central location. The top strap  312  can include two portions or halves that are adjustably connected. The adjustment mechanism  382  includes a male component and a female component that are adjusted to form the top strap  312 . The adjustment mechanism  382  can be incrementally and discretely adjusted. The headgear assembly  300  can include a baseball cap style adjustment arrangement including a button or post on one half or portion of the top strap that is received by any one of several spaced apart holes on the opposing half or portion of the top strap. The post can form a snap-fit or interference fit with the hole such that the adjustment mechanism  382 , and therefore the top strap  312 , is secure. Other types of fasteners are contemplated to provide the adjustment of the top strap  312 . The adjustment mechanism  382  is considered a fit and forget configuration in which the headgear assembly  300  is adjusted once and there may be no need to adjust on a regular basis. The adjustment mechanism  382  is integrally formed with top strap. 
     Referring to  FIG. 13 , the side arms  302  includes two segments  378 ,  380 . The two segments  378 ,  380  form an elbow, bend, or dog-leg. The segment  378  extends across the user&#39;s cheek in use. The side arms  302  are straighter across the user&#39;s cheeks than with headgear assembly  100 . The segment  380  bends upwards towards the pivot connection  356 . This two segment construction allows a force vector to be applied to the interface  10  closer to the chin region. This two segment construction counteracts blow-off forces and minimizes leaks in this area. The construction also allows the interface  10  to pivot at a location close to the center of the interface  10  which allows the amount of engagement between the interface  10  and the user&#39;s nose to be adjustable. 
     The adjustment mechanism  304  allows for incremental adjustment of the position of the interface  10  relative to the headgear assembly  300 . The adjustment mechanism  304  includes a female component  338  that is integrally formed at a forward and lower end of the side arms  302 . The adjustment mechanism  304  includes a male component  348  that is connected to the interface  10  by the pivot connection  356 . The female component  338  includes a guide loop  384  at its forward end. The guide loop  384  is configured to receive the male component  348  and guide the male component  348  into alignment with the female component  338 . The guide loop  384  also prevents rotation of the male component  348  relative to the female component  338  so that forces can be effectively transferred from the interface  10  to the headgear assembly  300 . The guide loop  384  limits or prevents the male component  348  from being completely disconnected from the female component  338 . The guide loop  384  provides friction to maintain or catch the male component  348  relative to the female component  338 . The guide loop  384  limits or prevents disassembly of the adjustment mechanism  304 . However, other suitable types of anti-rotate arrangements could also be used. 
     The adjustment mechanism  304  allows for incremental adjustment between the side arms  202  and the interface  10 . The male component  348  includes a button or post that is configured to be received in one of a plurality of apertures in the female component  338  to provide a baseball cap style adjustment arrangement. The post can form a snap-fit or interference fit with the aperture or hole such that the adjustment mechanism  304 , and therefore the side arm  202 , is secured in an adjusted position. The adjustment mechanism  304  includes multiple buttons or posts. The adjustment mechanism  304  includes a hook and loop fastener. Other configurations of fasteners are contemplated for the male component  348  and the female component  338 . The adjustment mechanism  304  can be incrementally and discretely adjusted. The adjustment mechanism  304  is considered a fit and forget configuration in which the headgear assembly  300  is adjusted once and there may be no need to adjust on a regular basis. Once the adjustment mechanisms  304 ,  382  are fitted to the user, the user pulls on the headgear assembly  300  like baseball cap. The user places the interface  10  in position and slides the top strap  312  around the crown of the head. Alternatively, the user places top strap  312  around the crown of the head and slides the interface  10  in position. 
       FIG. 14A  illustrates the interface  20  and a headgear assembly  400  including a ratchet style adjustment mechanism  404 . The headgear assembly  400  can be substantially the same as the headgear assembly  100  except as described below. Thus, any features not specifically described can be substantially the same as or similar to corresponding features of the headgear assembly  100  or other headgear assemblies described herein, or can be of another suitable arrangement. The headgear assembly  400  can include any features of the headgear assemblies described herein. While only one side arm  402  is shown in  FIGS. 14A-15 , the other side arm  402  can have the same or similar features and can be a mirror image of the illustrated side arm  402 . 
     The headgear assembly  400  includes a chin strap  410 , a top strap  412 , and a rear strap  414 . The headgear assembly  400  includes the side arm  402 . The chin strap  410  has a constant width. The top strap  412  has a constant width. The rear strap  414  has a constant width. In some embodiments, the chin strap  410  does not have a constant width. In some embodiments, the top strap  412  does not have a constant width. In some embodiments, the rear strap  414  does not have a constant width. 
     The side arm  402  includes an upper end  416  and a lower end  418 . The upper end  416  is bifurcated into a top strap connection point  420  and a rear strap connection point  422 . The side arm  402  includes an ear arch  424 . The ear arch  424  passes above the ear of the user in use. The side arm  402  includes a mid-section  426  between the upper end  416  and the lower end  418 . The side arm  102  includes a cheek curve  428 . The cheek curve  428  passes near the cheekbone of the user in use. The lower end  418  includes a chin strap connection point  430 . The lower end  418  couples to the adjustment mechanism  404 . 
     The adjustment mechanism  404  comprises a ratchet or cable tie type mechanism. The adjustment mechanism  404  provides incremental adjustment of the length between the side arms  402  and a connecting member  408 . The adjustment mechanism  404  provides incremental adjustment of the position of the interface  10 ,  20  relative to the headgear assembly  400 . The adjustment mechanism  404  includes male component  448 . The male component  448  couples to or extends from the lower end  418  of the side arm  402 . The male component  448  includes a plurality of teeth. The male component  448  can be integrally formed with the side arms  402  by means such as intra-moulding, as described herein. 
     The adjustment mechanism  404  includes female component  438 . The female component  438  couples to the connecting member  408 . The female component  438  includes a pawl inside a housing that engages one or more of the teeth of the male component. In other arrangements, the female component could include a cam lock member that provides infinite adjustability. In some embodiments, the arrangement of the adjustment mechanism  404  is reversed. The male component  448  is formed in or with the connecting member  408 . The female component  438  is formed in or with the side arms  402 . 
     For the full-face under-nose interface  20 , the male component  448  is angled downwards away from the user&#39;s face, in use, as shown in  FIG. 14A . The male component  448  is angled in a forward direction in comparison to the full-face over-nose interface  10  of  FIG. 14B . For the full-face over-nose interface  10 , the male component  448  is more horizontal. The lower ends  418  of the side arms  402  are close to horizontal. In some methods of use, variation will occur for differing cranial and/or facial geometries. In some methods of use, variation will occur for different interfaces. The configuration of the adjustment mechanism  404 , including the male component  448 , allows the headgear assembly  400  to apply a force to the interface  10 ,  20  in order to counteract blow-off forces. The downwardly angled male component  448  of  FIGS. 14A and 15  allow the headgear assembly  400  to apply an upwardly direction force to the interface  20  in order to increase engagement between the interface  20  and the under-side of the user&#39;s nose and improve the seal. 
     Referring to  FIG. 15 , the connecting member  408  includes two segments  478 ,  480 . The two segments  478 ,  480  form an elbow, bend, or dog-leg. The segment  480  bends upwards towards the pivot connection  456 . This two segment construction allows a force vector to be applied to the interface  20  at chin height, counteracts blow-off forces, minimizes leaks in this area, and allows the interface  20  to pivot at a location close to the center of the interface  20 . The two segments  478 ,  480  direct headgear forces back up towards the centrally located pivot connection  256 . 
       FIGS. 16A-16B  illustrates a headgear assembly  500  including a rail adjustment mechanism  504 . The headgear assembly  500  can be substantially the same as the headgear assembly  100  except as described below. Thus, any features not specifically described can be substantially the same as or similar to corresponding features of the headgear assembly  100  or other headgear assemblies described herein, or can be of another suitable arrangement. The headgear assembly  500  can include any features of the headgear assemblies described herein. While only one side arm  502  is shown in  FIGS. 16A-16B , the other side arm  502  of the headgear assembly  500  can have the same or similar features and can be a mirror image of the illustrated side arm  502 . The headgear assembly  500  can include any straps described herein.  FIG. 16A  is a front side view of the side arm  502 .  FIG. 16B  is a back side view of the side arm  502 . The side arm  502  includes a lower end  518 . The lower end  518  includes a chin strap connection point  530  and a support  532 . The headgear assembly  500  includes the connecting member  508 . 
     The adjustment mechanism  504  is another embodiment of an adjustment mechanism that can replace the adjustment mechanism  104  of headgear assembly  100  and any adjustment mechanism described herein. The adjustment mechanism  504  comprises two sets of interlocking rails  586 ,  588  that connect the lower forward end of the side arms  502  and the connecting member  508 .  FIG. 16C  is the cross-sectional view of the two sets of interlocking rails  586 ,  588  along line C-C in  FIG. 16B . The first set of interlocking rails  586  is along the upper edge of the connecting member  508  and the second set of interlocking rails  588  is along the lower edge of the connecting member. 
     The support  532  has a pair of tracks  590  that protrude from an internal surface of the support  532 . Each of the tracks  590  comprises a pair of opposing rails  592 ,  594  that form an elongate channel or female component of the adjustment mechanism  504 . The connecting member  508  has a pair of single rails  596  that protrude from an internal surface of connecting member  508 . The single rails  596  are spaced apart, with one on each elongate edge of the connecting member  508 . Each of the single rails  596  is received and retained in the channel of one of the tracks  590 . The reverse configuration of the support  532  and the connecting member  508  is contemplated. The second set of interlocking rails  588  along the lower edge can have the same configuration or a different configuration as the first set of interlocking rails  586  along the upper edge. 
     The two sets of interlocking rails  586 ,  588  can include one or more features to retain or interlock the tracks  590  and the single rails  596 . The tracks  590  have a flange that engages with a corresponding flange of the single rail  596  to retain the single rail  596  within the channel of the tracks  590 . Each opposing rail  592 ,  594  has a flange and the corresponding single rail  596  has two flanges. In some embodiments, at least one opposing rail  592 ,  594  has a flange and the corresponding single rail  596  has at least one flange. The two sets of interlocking rails  586 ,  588  are designed to permit sliding there between but limit disengagement. The two sets of interlocking rails  586 ,  588  are disposed horizontally in use. The two sets of interlocking rails  586 ,  588  include a male component designed to be received in and inlock with a female component. The tracks  590  function as the female component and the single rail  596  functions as the male component of the adjustment mechanism  504 . In some embodiments, one set of interlocking rails is utilized. The two sets of interlocking rails  586 ,  588  allow the connecting member  508  to slide relative to the side arm  502 . Other configurations are contemplated for creating a sliding connection. 
     Referring back to  FIGS. 16A and 16B , the headgear assembly  500  includes a biasing elastic  598 . The biasing elastic  598  couples to a forward end of the connecting member  508  and a rear end of the side arms  502 . The biasing elastic  598  can have any connection point between the connecting member  508  and the side arms  502 . The biasing elastic  598  is configured to bias the adjustment mechanism  504  towards an un-extended or neutral position as shown in  FIG. 16A .  FIG. 16B  illustrates the biasing member  598  extending beyond the neutral position. The biasing elastic  598  has a longer length in  FIG. 16B  than in  FIG. 16A . The biasing elastic  598  extends as the interlocking rail  588  coupled to the connecting member  508  slides along the interlocking rail  586  coupled to the side arm  502  in a direction that increases a length of the adjustment mechanism  504 . The biasing elastic  598  has the effect of pulling the interface  10 ,  20  towards the user&#39;s face to increase the sealing force. In some arrangements, the biasing elastic  598  may have relatively flat force extension profile so that the sealing force applied by the biasing elastic  598  is not overly large when the user&#39;s head is larger. In some arrangements, the biasing elastic  598  could be omitted and a retention mechanism could be employed to secure the adjustment mechanism  504  in an adjusted position. 
       FIGS. 17A-17B  illustrates a headgear assembly  600  including a side arm  602  with a first or an upper member  692  and a second or a lower member  694 . The headgear assembly  600  can be substantially the same as the headgear assembly  100  except as described below. Thus, any features not specifically described can be substantially the same as or similar to corresponding features of the headgear assembly  100  or other headgear assemblies described herein, or can be of another suitable arrangement. The headgear assembly  600  can include any features of the headgear assemblies described herein. While only one side arm  602  is shown in  FIGS. 17A-17B , the other side arm  602  of the headgear assembly  600  can have the same or similar features and can be a mirror image of the illustrated side arm  602 . While interface  10  is shown, any interface can be used with headgear assembly  600 . 
     The side arm  602  includes the upper member  692 . The upper member  692  of the side arm  602  includes an upper end  616 . The upper end  616  is bifurcated into a top strap connection point  620  and a rear strap connection point  622 . The top strap connection point  620  and the rear strap connection point  622  form an angle there between. The top strap connection point  620  is substantially vertical and the rear strap connection point  622  is substantially horizontal. The upper member  692  of the side arm  602  includes an ear arch  624 . The ear arch  624  passes above the ear of the user in use. The upper member  692  of the side arm  602  includes a mid-section  626 . The head gear assembly  600  includes a top strap  612  and a rear strap  614 . 
     The side arm  602  includes the lower member  694 .  FIG. 17B  illustrates the lower member  694 . The lower member  694  is formed as an elongate extension of a connecting member  608 . The lower member  694  extends towards the user&#39;s lower jaw and a location below the user&#39;s ears. The connecting member  608  is integrally formed with the lower member  694 . In some embodiments, the connecting member  608  is not integrally formed with the lower member  694 . In some embodiments, the connecting member  608  forms an adjustment mechanism with the side arm  602 , according to any of the embodiments described herein. The connecting member  608  forms a rotational adjustment mechanism or pivot connection  656  with the interface  10 . 
     The upper member  692  and the lower member  694  include a second rotational adjustment mechanism or pivot connection  698 . The side arm  602  is formed by the upper member  692  and the lower members  694  that are pivotally coupled by the pivot connection  698 . The upper member  692  and the lower members  694  are separate components. The forward lower end of the upper member  692  is pivotally coupled to a mid-point of the lower member  694 . In some embodiments, the upper member  692  is pivotally coupled to the lower member  694  at a point other than a mid-point (e.g., closer to the interface  10  than the midpoint, farther from interface than the midpoint, etc.). 
     The lower member  694  of the side arm  602  includes a first chin strap connection point  630  and a second chin strap connection point  670 . The first and second chin strap connection points  630 ,  670  are spaced along the length of the lower member  694 . The first chin strap connection point  630  is forward of the connection with the upper member  692  and the second chin strap connection point  670  is at or near a rear or free end of the lower member  694 . The first chin strap connection point  630  is closer to the interface  10  than the second chin strap connection point  670 . The first chin strap connection point  630  and the second chin strap connection point  670  can form an angle there between. The angle can be approximately 180 degrees (e.g., 170 degrees, 180 degrees, 190 degrees, 200 degrees, 210 degrees, etc.). The first chin strap connection point  630  and the second chin strap connection point  670  are located on opposite sides of the lower member  690 . In some embodiments, the first chin strap connection point  630  and the second chin strap connection point  670  are located on the same side of the lower member  690 . 
     The head gear assembly  600  includes a first chin strap  610  designed to couple to the first chin strap connection point  630 . The head gear assembly  600  includes a second chin strap  696  designed to couple to the second chin strap connection point  670 . The lower member  694  has two chin straps  610 ,  696  adjustably attached to the lower member  690 . The first chin strap  610  extends under the user&#39;s chin. The second chin strap  696  is spaced from the first chin strap. The second chin strap  696  extends at least partially around the user&#39;s neck. 
     The first chin strap  610  is near the mid-point of the lower member  694 . In some embodiments, the first chin strap  610  can be attached at any location along the lower member  694 . The first chin strap  610  can be attached at any location forward of the second chin strap  696 . The first chin strap  610  is attached at a point forward of the pivot connection  698 . The second chin strap  696  is attached at a point rearward of the pivot connection  698 . The second chin strap  696  is attached at a rear end of the lower member  694 . 
     The lower member  694  forms a lever arm where tightening the second chin strap  696  causes the lower member  694  to rotate anti-clockwise (as indicated by the arrow in  FIG. 17A ) and further engage the interface  10  with the user&#39;s face. In other arrangements, other mechanisms for rotating the lower member  694  relative to the upper member  692  can be employed in the place of or in addition to the second chin strap  696 . For example, a length-adjustable strap or strut can be used to adjust a relative rotational position between the upper member  692  and the lower member  694 . 
       FIG. 18  illustrates an interface  30  and a headgear assembly  700  including a side arm  702  with an upper portion  792  and a lower portion  794 . The headgear assembly  700  can be substantially the same as the headgear assembly  100  except as described below. Thus, any features not specifically described can be substantially the same as or similar to corresponding features of the headgear assembly  100  or other headgear assemblies described herein, or can be of another suitable arrangement. The headgear assembly  700  can include any features of the headgear assemblies described herein. While only one side arm  702  is shown in  FIG. 18 , the other side arm  702  can have the same or similar features and can be a mirror image of the illustrated side arm  702 . The headgear assembly  700  includes the integrally formed upper portion  792  and top strap  712 . The headgear assembly  700  includes the rear strap  714 . The headgear assembly  700  includes the integrally formed lower portion  794  and chin strap  710 . 
       FIG. 18  shows an interface assembly for use in respiratory therapy, the interface assembly including the interface  30  and the headgear assembly  700 . Each side of the headgear assembly  700  the upper portion  792  connected to the interface  30  and adapted to extend from the interface  30  to a location above a user&#39;s ear and the lower portion  794  having a first end that connects to the upper portion  792  and a second end that connects to the interface  30  below the connection of the upper portion  792  to the interface  30 . The connection location of at least one of the ends of the lower portion  794  is adjustable. The connection location of at least one of the ends of the lower portion is discretely adjustable. 
       FIG. 18  illustrates a plurality of connection points  32  on the interface  30 . The upper portions  792  are removably connected to any one of the plurality of connection points  32  on the interface  30 . The upper portions  792  include a post and aperture snap-fit connection. The upper portions  792  include the aperture and the interface  30  includes the post. In some embodiments, the upper portions  792  include the post and the interface  30  includes the apertures. Other configurations are contemplated to couple the upper portions  792  and the interface  30 . In some embodiments, the upper portions  792  and the interface  30  include magnets. The upper portions  792  and the interface  30  are removably joined. In some embodiments, the upper portions  792  and the interface  30  are permanently joined. The upper portions  792  and/or the interface  30  include extra connection points  32 . The extra holes and/or connection points  32  in a snap fit arrangement may be plugged with inserts  34  to maintain an air tight breathing chamber within the interface  30 . The connection points  32  protrude from an outer surface of the interface  30 . In some embodiments, the connection points  32  can allow the interface  30  and upper side arm  702  to pivot relative to each other. The upper portions  792  are semi-rigid. 
     The lower portions  794  are removably connected to any one of a plurality of connection points  32  on the interface  30 . The lower portion  794  can connect via a snap fit with one or more posts and one or more holes. The lower portion  794  can connect via magnets. The lower portion  794  can connect via any other couplings or connection means. The lower portion  794  and the connection points  32  allow for incremental adjustment of the height of the lower portion  794  relative to the interface  30  and/or upper portion  792 . The lower portion  794  can be incrementally and discretely adjusted. The lower portion  794  and the connection points  32  can include an adjustment arrangement including a button or post connection points  32  that is received by any one of a several spaced apart holes in the lower portion  794 . The post can form a snap-fit or interference fit with the hole such that the lower portion  794  is secure. Other types of fasteners are contemplated to provide the adjustment of the lower portion  794 . The lower portion  794  and the connection points  32  adjustment arrangement is considered a fit and forget configuration in which the lower portion  794  is adjusted once and there may be no need to adjust on a regular basis. 
     The lower portion  794  is connected to the upper portions  792  at a strap junction  796 . The strap junction  796  is formed where the top strap  712  diverges from the upper portions  792 . When the lower portion  794  is connected between the strap junction  796  and the interface  30 , any pivoting motion of the interface  10  relative to the upper portions  792  is reduced or prevented. The lower portion  794  connects to the upper portions  792  via any one of a plurality of connection points  798  at the strap junction  796 . In some methods of use, the lower portion  794  can be connected to only one connection point  798  after the lower portion  794  is connected to the interface  30  based on the fit to the user. The connection between the lower portions  794  and the strap junctions  796  allows the lower portions  794  to pivot relative to the upper portions  792 . The chin strap  710  extends between the opposing lower portions  794 . The plurality of connection points  32  on the interface  30  and the plurality of connection points  798  at the strap junction  796  allow the angle and distance between the upper portion  792  and lower portion  794  to be adjusted. As an example, increasing the angle between the upper portion  792  and lower portion  794  will reduce the distance between the strap junction  796  and a chin region of the interface  30  thus increasing engagement and sealing force between the chin region and a user&#39;s chin. As another example, decreasing the angle between the upper portion  792  and lower portion  794  will increase the distance between the strap junction  796  and a chin region of the interface  30  thus decreasing engagement and sealing force between the chin region and a user&#39;s chin. Adjusting the distance between the upper portion  792  and lower portion  794  can also produce differences in the engagement and the sealing force. 
     When fitting the interface  30 , the lower portions  794  are preferably disconnected from the strap junction  796  such that the interface  30  and rest of the headgear  700  can be fitted to the user&#39;s head. The interface  30  is positioned and then the lower portions  794  along with the chin strap  710  can be pivoted/swung upwards into engagement and then connected to the strap junction  796 . 
       FIGS. 19A-19B  illustrate an interface  10  and a headgear assembly  800  including a side arm  802  with an upper side arm  892  and a lower side arm  894 . The headgear assembly  800  includes the integrally formed upper side arm  892  and a top strap  812 . The headgear assembly  800  includes a rear strap  814 . The headgear assembly  800  includes a chin strap  810 . The upper and lower side arms  892 ,  894  are pivotally coupled to the interface  10 . While only one side arm  802  is shown in  FIG. 19A-19B , the other side arm  802  can have the same or similar features and can be a mirror image of the illustrated side arm  802 . The headgear assembly  800  can be substantially the same as the headgear assembly  100  except as described below. The headgear assembly  800  can be substantially the same or similar to the headgear assembly  300  described herein. Thus, any features not specifically described can be substantially the same as or similar to corresponding features of the headgear assembly  100  or other headgear assemblies described herein, or can be of another suitable arrangement. The headgear assembly  800  can include any features of the headgear assemblies described herein. 
     The lower side arm  894  is connected to the upper side arm  892  at a strap junction  899 . The strap junction  899  is at a location spaced from where the top strap  812  diverges from the upper side arm  892 . The strap junction  899  is located forward of the point where the top strap  812  diverges from the upper side arm  892 . When the lower side arm  894  is connected between the strap junction  899  and the interface  10 , any pivoting motion of the interface  10  relative to the upper side arm  892  is reduced or prevented. The lower side arm  894  connects to the upper side arm  892  via a fastener at the strap junction  899 . The fastener can be a hook and loop fastener or any other adjustment mechanism described herein. The connection between the lower side arms  894  and the strap junctions  899  allows the lower side arms  894  to pivot relative to the upper side arm  892 . 
     The chin strap  810  is removably coupled to the lower side arm  894 .  FIG. 19A  illustrates the chin strap  810  in a first configuration.  FIG. 19A  illustrates the chin strap  810  extending from a midpoint of the lower side arm  894 . The chin strap  810  extends between the opposing lower side arms  894  and under the chin of the patient. 
       FIG. 19B  illustrates the chin strap  810  in a second configuration. The chin strap  810  is connected to the rear ends of the lower side arms  894  to form a neck strap that extends around the neck of the user. The rear ends of the lower arms  894  are disconnected from a strap junction  899  and pivoted downwards towards the user&#39;s neck. The rear end of the lower side arm  894  can include a fastener that enables the lower side arm  894  to be connected to the strap junction  899  or the lateral ends of the chin strap  810 . 
       FIGS. 20 and 21  illustrate an interface  10  and a headgear assembly  900  including integrally formed side arms  902 , chin strap  910 , top strap  912 , and rear strap  914 . The headgear assembly  900  can be substantially the same as the headgear assembly  100 , 200 , 300 , except as described below. Thus, any features not specifically described can be substantially the same as or similar to corresponding features of the headgear assembly  100 , 200 , 300  or other headgear assemblies described herein, or can be of another suitable arrangement. The headgear assembly  900  can include any features of the headgear assemblies described herein. While only one side of headgear assembly  900  is shown in  FIGS. 20-21 , the other side can have the same or similar features and can be the same or similar to the illustrated side depicted in  FIGS. 20-21 . The side arms  902  on either side of the headgear assembly  900  rest on opposite sides of the user&#39;s face, extend towards the middle of the user&#39;s face, and form a continuous loop, forming yoke portion  940  that engages interface  10  as described below. As with the headgear assembly  300  disclosed above, the side strap  902  is located above the ears and does not come into contact with the ears. As described herein, the side arms  902  are integrally formed with the chin strap  910 , top strap  912 , and rear strap  914 . The side arm  902  includes a rear strap connection point  922  and a chin strap connection point  930 , at which points the straps may be continuous with each other, formed by a single moulding process for example, or may be separate components that are permanently attached. 
     The headgear assembly  900  includes the integrally formed side arms  902 , chin strap  910 , top strap  912 , and rear strap  914 . The side arms  902 , chin strap  910 , top strap  912 , and rear strap  914  are integrally formed as a single component. Any or each of the side arms  902 , the chin strap  910 , the top strap  912 , and/or the rear strap  914  can include a textile covering. The textile covering covers at least a portion of the side arms  902 , the chin strap  910 , the top strap  912 , and/or the rear strap  914 . In some embodiments, the textile covering covers the side arms  902 , the chin strap  910 , the top strap  912 , and/or the rear strap  914  in their entirety. The side arms  902 , the chin strap  910 , the top strap  912 , and/or the rear strap  914  are intra-moulded. In some methods of manufacturing of the side arms  902 , the chin strap  910 , the top strap  912 , and/or the rear strap  914 , molten plastic is injected into one or more textile tubes, including one or more interconnected textile tubes, each having a lumen connected at least in part to the lumen of an adjacent tube. The plastic and the textile tubes are a unitary structure. The side arms  902  and the top strap  912  can be separately formed and later joined at connection point  922 . The side arms  902  and the chin strap  910  can be separately formed and later joined at connection point  930 . The side arms  902  and the rear strap  914  can be continuous, or can be separately formed and later joined at or near connection point  922 . Each connection may be formed by an over-moulding process or an intra-moulding process. 
     The headgear assembly  900  is considered a fit and forget configuration in which the headgear assembly  900  is fitted once by selecting an appropriate size and configuration and there is no need to adjust it further. Accordingly, the side arms  902 , the chin strap  910 , the top strap  912 , and/or the rear strap  914  are of fixed length and are not adjustable. Fitting on the user&#39;s head and donning/doffing may be possible by pivoting the chin strap forward, away from the user&#39;s neck. The headgear assembly  900  may be permanently or removably attached to interface  10 , either to a mask that forms interface  10 , or a mask frame that forms a component of interface  10 . Removable attachment allows for easy disassembly and cleaning of the headgear assembly  900  and interface  10 . Removable attachment may be achieved by various mechanisms such as snap fit or friction-fit of yoke portion  940  into or onto corresponding snap fit or friction fit features of interface  10 . In alternative embodiments, any adjustment mechanism described herein, including but not limited to adjustment mechanisms  304  and/or  382 , may be formed within one or more of the the chin strap  910 , the top strap  912 , and/or the rear strap  914 . 
     There are several advantages associated with one or more embodiments of the headgear described herein. The headgear is used with any interface, such as a full-face mask. An advantage is that the headgear simplifies fitting. The headgear is easier to fit than traditional four point headgear. The headgear has fewer adjustments. The headgear can be positioned without undoing all of the connections. For instance, the headgear includes baseball cap style fitting, wherein the headgear is positioned in a single motion similar to putting on a baseball cap. The fit is easy, in part, because of the absence of a lower strap that passes below the user&#39;s ears. 
     An advantage is that the headgear of one or more embodiments described herein minimizes size and bulk compared with other commercially available headgear. The user perceives less straps and/or components on the front of the interface  10 ,  20 ,  30 , which makes the interface  10 ,  20 ,  30  look less complicated and obtrusive. An advantage is that the headgear can be intuitive to use based on the connection between the headgear and the interface. In some embodiments, the headgear has a single point connection between the interface and each side of the headgear. The single point of connection can include various features and improvements. The single point of connection is a pivot connection. The single point of connection counteracts blow off forces. The single point of connection includes a component which is horizontal in use. The single point of connection is adjustable to bring the headgear toward and away from the interface. In some embodiments, the headgear has a two point connection between the interface and each side of the headgear. The two point connection can include various features and improvements. The two points of connection reduce or prevent pivoting of the headgear. 
     An advantage of one or more embodiments described herein is that the headgear keeps headgear straps away from the user&#39;s eyes. The headgear passes along the sides of the face of the user. The headgear passes along the user&#39;s cheeks. The headgear passes over the user&#39;s ears. The headgear passes along the crown of the head. The headgear passes along the back of the head. The headgear passes under the chin of the user. The headgear does not pass along the forehead of the user. The headgear does not pass across the eyes of the user. 
     An advantage of one or more embodiments described herein is that the semi-rigid side arms allow sufficient force vectors to be applied to the interface in controlled directions. The semi-rigid side arms extend along the sides of the face of the user. The semi-rigid side arms prevent or limit extension in two directions, but may allow flexing in a third direction. The third direction can allow flexing toward and away from the user&#39;s cheeks during use. The semi-rigid side arms prevent or limit extension in a horizontal and a vertical direction. The semi-rigid side arms allow sufficient force vectors to be applied to the interface to enable a good seal between the user&#39;s face and the interface. The semi-rigid side arms can provide a good seal, despite a single attachment point on each side. The semi-rigid side arms reduce or limit movement between the headgear assembly and the interface. The semi-rigid side arms are vertically rigid in use. The semi-rigid side arms are horizontally rigid in use. The rigid side arms can flex toward and away from the user&#39;s cheeks in use. 
     An advantage of one or more embodiments described herein is that the headgear assembly retains its shape when not in use. The headgear assembly is held in an open configuration, by the semi-rigid side arms, when the headgear assembly is not in use. The open configuration improves the ease with which the headgear assembly and interface can be fitted to a user. The open configuration can also improve usability as the straps do not tangle as easily. In the open configuration, the user can visualize how to position and use the headgear assembly. 
     An advantage of one or more embodiments described herein is that the headgear assembly includes semi-rigid side arms which eliminate the need for a forehead support. The side arms include a semi-rigid plastic material. In some embodiments, the side arms include any semi-rigid material. The headgear assembly provides a clear line of sight which makes the headgear assembly feel less intrusive to the user. The headgear assembly also allows the user to wear glasses while wearing the headgear assembly due to the elimination of the forehead support. The semi-rigid arms are placed to counteract forces. In use, the semi-rigid side arms are placed above the ears of the user. In use, the semi-rigid side arms are placed down the cheeks of the user. The semi-rigid side arms are held in position with the top strap and the rear strap. The top strap and the rear strap include a wider section. The semi-rigid side arms are held in position by the chin strap. The chin strap allows for the elimination of the forehead support. 
     An advantage of one or more embodiments described herein is that the headgear assembly includes an adjustable or pivotable connection to the interface. The headgear assembly includes a connecting member. The connecting member includes a pivot connection. In some embodiments, the connecting member does not include a pivot connection. An advantage of one or more embodiments described herein is that the headgear assembly includes a connection to the interface to counteract forces. The connecting member is substantially horizontal in use. The connecting member is substantially horizontal to counteract blow off forces. The blow off forces are forces that act to separate the interface from the user. The interface in connected to an air inlet. The air delivered to the air inlet, and subsequently to the user, exerts a pressure on the face of the user. This pressure can be directed from the air inlet toward the user in a horizontal direction. The interface tends to move away from the user in a horizontal direction, if the blow off forces are not counteracted. The horizontal portion of the connecting member and/or the horizontal portion of the side arm can reduce or prevent the separation between the interface and the user. 
     An advantage of one or more embodiments described herein is that the headgear assembly includes a chin strap. The blow off forces can function as forces that cause the chin strap to ride up. The chin strap, in combination with the horizontal portion of the connecting member and/or side arm, can reduce or prevent the separation between the interface and the user. The chin strap prevents movement of the headgear assembly. In some embodiments, the chin strap is the only strap that is disconnected or adjusted to remove the headgear assembly. In some embodiments, the chin strap is the only strap that is connected by the user in use. The rear strap and the top strap have a set-and-forget configuration. The rear strap and the top strap stay connected when the user removes the headgear assembly. In some embodiments, the chin strap is convertible to a neck strap. The chin strap can help prevent the user&#39;s jaw from dropping and causing leaks. 
     An advantage of one or more embodiments described herein is that the headgear includes an adjustment mechanism. The adjustment mechanism provides a linear adjustment between the semi-rigid side arms and the interface. The adjustment mechanism provides forward and backward adjustment such as through an adjustment mechanism or biasing elastic. The adjustment mechanism adjusts to fit a variety of faces. The adjustment mechanism provides a telescoping arrangement. The adjustment mechanism extends the rigid connection to the interface. The adjustment mechanism extends from the side arm in a substantially horizontal direction. Soft straps can allow the interface to move, but the semi-rigid side arms and additional rigid components such as the connecting member can reduce or prevent this movement. The adjustment mechanism can be considered a translation mechanism. The adjustment mechanism can allow the headgear assembly to translate relative to the interface. The adjustment mechanism includes a ratchet. The adjustment mechanism includes two interlocking rails. The adjustment mechanism includes two telescoping members. The adjustment mechanism includes a biasing member to bias the interface and the headgear assembly toward each other. 
     An advantage of one or more embodiments described herein is that the headgear assembly includes headgear adjustment technology. The adjustment mechanism is self-fit in which the adjustment mechanism moves the interface and the headgear assembly toward each other. The headgear adjustment technology includes a first elongate member and a second elongate member slidably engaged with the first elongate member. The first elongate member and the second elongate member are configured to enable adjustment of the length of the adjustment mechanism by changing an amount of overlap between the first and second elongate members. The headgear adjustment technology includes a restriction mechanism or biasing member configured to provide resistance against decreasing the amount of overlap between the first and second elongate members. The headgear adjustment technology includes a retraction means configured to apply a retraction force to the first elongate member that increases the amount of overlap between the first and second elongate members. The adjustment mechanism includes a direction lock. The adjustment mechanism allows for retraction. The adjustment mechanism includes a biasing elastic to automatically fit the user. The adjustment mechanism can overcome a locking force manually. The adjustment mechanism is calibrated to resist blow off. 
     An advantage of one or more embodiments described herein is that the headgear assembly includes a pivot mechanism. The pivot mechanism is located at the connection between the connecting member and the interface. The pivot mechanism allows deliberate angular adjustment of the interface. The pivot mechanism maintains the angular adjustment between the interface and the headgear assembly. The pivot mechanism maintains the relative position between the interface and the headgear assembly through friction. The pivot is located about a midpoint of the interface. The pivot is at a center of rotation of the interface. The pivot is positioned to reduce inadvertent torqueing or movement of the interface. The pivot is positioned such that the interface can move toward the nose or the chin. 
     An advantage of one or more embodiments described herein is that the headgear assembly includes a pivot that is vertically higher than the adjustment mechanism. The headgear assembly includes two segments that form an upward extension of semi-rigid side arm. The two segments position the semi-rigid side arm below the pivot. The two segments position the adjustment mechanism below the pivot. The two segments position the male component of the adjustment mechanism below the pivot. The two segments position the adjustment mechanism horizontally. The two segments position the extension of the side arm horizontally. This position can balance the forces exerted on the interface. This position can enable the pivot to be centrally located. This position can enable the pivot to be located at a center of rotation of the interface. This position can reduce torque of the interface due to blow off forces. The pivot axes are centrally located on the lateral sides of the interface. In some embodiments, the pivot axes are located above the air inlet. 
     An advantage of one or more embodiments described herein is that the headgear includes a portion of the semi-rigid side arm positioned below the air inlet. The pivot mechanism is positioned near the air inlet. The connecting member includes two segments which enable the connecting member to be positioned at least partially below the air inlet. The semi-rigid side arm includes two segments which enable the semi-rigid side arm to be positioned below the air inlet. The two segments can include an elbow or bend with a first segment extending downward and/or backward and a second segment extending horizontally. The forces from the air inlet are horizontal and the counteracting forces from the semi-rigid side arm are horizontal. A lower portion of the semi-rigid side arm is below the midpoint or geometric center of the interface. The semi-rigid side arm is below the geometric center of the interface. The portion of the semi-rigid side arm is positioned low on the user&#39;s face. 
     An advantage of one or more embodiments described herein is that the headgear assembly includes a transition relative to the pivot axis. The pivot axes are centrally located on the lateral sides of the interface. The pivot axes are skewed relative to a vertical plane. The pivot axes are skewed relative to a horizontal plane. The lateral sides of the interface can be angled to form a triangle. The pivot axes are perpendicular to the lateral sides. The transition is a rigid twist in the connecting member. The transition positions the adjustment mechanism to be horizontal in use. The transition positions the adjustment mechanism to lie in a vertical plane. The transition positions the pull tab loop to lie in a vertical plane. The transition can enable free, horizontal movement of the components of the adjustment mechanism. The transition provides an offset from the interface. The transition allows for a flush pivot connection with the interface while orienting other components such as the adjustment mechanism in a desired orientation. 
     An advantage of one or more embodiments described herein is that the headgear assembly includes one or more intra-moulded features. The semi-rigid side arms are intra-moulded. A textile material is formed into a tube and a molten plastic is injected in between the tube. The intra-moulded side arm includes a cover textile surrounding a plastic core. The intra-moulded feature can be an integrated plastic with textile covering. The cover layer can be constructed from a soft fabric, textile, foam or similar cushioning materials. The core may be formed by inserting a semi-rigid plastic into the cavity of the cover layer. The side arms and the top strap are intra-moulded. The side arms and the rear strap are intra-moulded. The intra-moulded component allows for adjustment. The intra-moulded component allows for discrete adjustment through one or more connection points or strap junctions. The intra-moulded component includes one or more guide loops. The guide loop restricts the pivot motion or rotation of the semi-rigid side arm. The guide loop maintains the rigidity of the side arm. 
     Any of the features of headgear assemblies described herein can be combined. Additional or alternative features include the following. In some embodiments, the headgear assembly is for a full-face or nasal interface. In some embodiments, the headgear includes a pair of opposing, semi-rigid side arms that extend between an interface and a location above the user&#39;s ears, across the user&#39;s cheeks. In some embodiments, each of the side arms is coupled to the interface at a single location. In some embodiments, the side arms are pivotally coupled to the interface. In some embodiments, a top strap is provided that extend between the side arms, over the top of a user&#39;s head. In some embodiments, a rear strap is provided that extends between the side arms, around the rear of the user&#39;s head. In some embodiments, a chin strap is provided that extends between the pair of side arms below the user&#39;s chin. In some embodiments, the headgear assembly includes an adjustment mechanism that allows the interface to move relative to the side arms. In some embodiments, the adjustment mechanism essentially allows adjustment of the length of the side arms. In some embodiments, the adjustment mechanism includes a pair of members or components that are telescopically engaged. 
     In some embodiments, the headgear assembly allows for rotation of the side arms. In some embodiments, the headgear assembly allows for translation of the side arms. In some embodiments, the headgear includes a pair of side arms. In some embodiments, each side arm includes a translational adjustment mechanism configured to allow translational adjustment of the side arm. In some embodiments, each side arm includes a rotating adjustment mechanism configured to allow rotational adjustment of the side arm. In some embodiments, the translational adjustment mechanism includes a pair of members or components that are telescopically engaged. In some embodiments, rotating adjustment mechanism includes a pivot connection. 
     In some embodiments, the headgear assembly includes two rotation or pivot points. In some embodiments, the headgear assembly includes two chin straps. In some embodiments, the headgear assembly is for a patient interface. In some embodiments, the headgear assembly includes a pair of side arms. In some embodiments, each side arm includes a first rotational adjustment mechanism configured to allow rotational adjustment of the side arm. In some embodiments, each side arm includes a second rotational adjustment mechanism configured to allow rotational adjustment of the side arm. In some embodiments, the first and second rotational adjustment mechanisms spaced apart along the side arm. In some embodiments, the headgear assembly includes a top strap, a rear strap and first and second chin straps. In some embodiments, the chin straps are spaced apart from each other. In some embodiments, the chin straps extend between the pair of side arms. 
     In some embodiments, the headgear assembly includes a transition. In some embodiments, the transition is between a pivot connection and a male component of a connection member. The transition twists to change the plane that the male component lies in. The upper edge is twisted outwards relative to the lower edge, so that the male component lies along a substantially vertical plane. In some embodiments, the headgear includes an upward extension of the side arm towards pivot point. 
     In some embodiments, the headgear includes two side arms. In some embodiments, each side of the headgear has a first side strap extending from an interface to a location above the user&#39;s ear. In some embodiments, each side of the headgear has a second side strap having a first end that connects to the first side strap and a second end that connects to the interface below the connection of the first side strap. In some embodiments, the connection locations of the ends of the second strap are discretely adjustable. In some embodiments, the headgear includes a strap that is reconfigurable between a chin strap and a rear neck strap.