A patient interface comprising: a plenum chamber pressurisable to a therapeutic pressure of at least 6 cmH 2 O above ambient air pressure, said plenum chamber including a plenum chamber inlet port sized and structured to receive a flow of air at the therapeutic pressure for breathing by a patient; a seal-forming structure constructed and arranged to form a seal with a region of the patient's face surrounding an entrance to the patient's airways, said seal-forming structure having a hole therein such that the flow of air at said therapeutic pressure is delivered to at least an entrance to the patient's nares, the seal-forming structure constructed and arranged to maintain said therapeutic pressure in the plenum chamber throughout the patient's respiratory cycle in use; and a positioning and stabilising structure to provide a force to hold a seal-forming structure in a therapeutically effective position on the patient's head, the positioning and stabilising structure comprising: at least one rigidized arm configured, in use, to be positioned adjacent to a cheek of the patient; and a strap removably received around the rigidized arm and configured to contact, in use, a posterior region of the patient's head, characterized in that the strap comprises: a first rigid coupling forming an opening to a cavity, the rigidized arm being positionable through the opening and into the cavity, the first rigid coupling having a mechanical connector that is configured to engage the rigidized arm and limit movement of the rigidized arm into and out of the cavity, a second rigid coupling spaced apart from an outer surface of the first rigid coupling, and a sleeve constructed from a flexible material, the sleeve being folded over the second rigid coupling and positioned between the first rigid coupling and the second rigid coupling. a plenum chamber pressurisable to a therapeutic pressure of at least 6 cmH 2 O above ambient air pressure, said plenum chamber including a plenum chamber inlet port sized and structured to receive a flow of air at the therapeutic pressure for breathing by a patient; a seal-forming structure constructed and arranged to form a seal with a region of the patient's face surrounding an entrance to the patient's airways, said seal-forming structure having a hole therein such that the flow of air at said therapeutic pressure is delivered to at least an entrance to the patient's nares, the seal-forming structure constructed and arranged to maintain said therapeutic pressure in the plenum chamber throughout the patient's respiratory cycle in use; and a positioning and stabilising structure to provide a force to hold a seal-forming structure in a therapeutically effective position on the patient's head, the positioning and stabilising structure comprising: at least one rigidized arm configured, in use, to be positioned adjacent to a cheek of the patient; and a strap removably received around the rigidized arm and configured to contact, in use, a posterior region of the patient's head, characterized in that the strap comprises: a first rigid coupling forming an opening to a cavity, the rigidized arm being positionable through the opening and into the cavity, the first rigid coupling having a mechanical connector that is configured to engage the rigidized arm and limit movement of the rigidized arm into and out of the cavity, a second rigid coupling spaced apart from an outer surface of the first rigid coupling, and a sleeve constructed from a flexible material, the sleeve being folded over the second rigid coupling and positioned between the first rigid coupling and the second rigid coupling. at least one rigidized arm configured, in use, to be positioned adjacent to a cheek of the patient; and a strap removably received around the rigidized arm and configured to contact, in use, a posterior region of the patient's head, characterized in that the strap comprises: a first rigid coupling forming an opening to a cavity, the rigidized arm being positionable through the opening and into the cavity, the first rigid coupling having a mechanical connector that is configured to engage the rigidized arm and limit movement of the rigidized arm into and out of the cavity, a second rigid coupling spaced apart from an outer surface of the first rigid coupling, and a sleeve constructed from a flexible material, the sleeve being folded over the second rigid coupling and positioned between the first rigid coupling and the second rigid coupling. a first rigid coupling forming an opening to a cavity, the rigidized arm being positionable through the opening and into the cavity, the first rigid coupling having a mechanical connector that is configured to engage the rigidized arm and limit movement of the rigidized arm into and out of the cavity, a second rigid coupling spaced apart from an outer surface of the first rigid coupling, and a sleeve constructed from a flexible material, the sleeve being folded over the second rigid coupling and positioned between the first rigid coupling and the second rigid coupling.