An adjustable trocar assembly comprising: a housing configured to facilitate insertion of one or more surgical tools into a patient's body; and an elongated tubular member extending distally from the housing and defining a longitudinal axis, the elongated tubular member including: a channel configured to facilitate passage of surgical instruments through the elongated tubular member; an adjustable portion configured to facilitate axial extension or axial retraction of the elongated tubular member, wherein the adjustable portion is defined by a plurality of adjacent extendable and retractable circular ridges centered along the longitudinal axis of the elongated tubular member, each of the circular ridges including a proximal end and a distal end, wherein the radius of the proximal end is less than the radius of the distal end to create a tapering effect along an external surface between adjacent ridges to allow for the proximal end to be partially inserted into the proximally adjacent circular ridge so that the minimum axial radius of the internal surface of the tubular member never decreases below the radius of the proximal end of each circular ridge; a collar of fixed diameter; and a rim of fixed diameter equal to the diameter of the collar; characterized by each of the circular ridges of the adjustable portion being operably coupled to one or more adjacent circular ridges of the plurality of circular ridges by a flexible material interconnecting adjacent circular ridges wherein each circular ridge includes a fold made by an excess of a small portion of the flexible material, the fold configured to collapse inward between adjacent circular ridges to facilitate partial insertion of one circular ridge into an adjacent circular ridge during retraction of the adjustable portion. a housing configured to facilitate insertion of one or more surgical tools into a patient's body; and an elongated tubular member extending distally from the housing and defining a longitudinal axis, the elongated tubular member including: a channel configured to facilitate passage of surgical instruments through the elongated tubular member; an adjustable portion configured to facilitate axial extension or axial retraction of the elongated tubular member, wherein the adjustable portion is defined by a plurality of adjacent extendable and retractable circular ridges centered along the longitudinal axis of the elongated tubular member, each of the circular ridges including a proximal end and a distal end, wherein the radius of the proximal end is less than the radius of the distal end to create a tapering effect along an external surface between adjacent ridges to allow for the proximal end to be partially inserted into the proximally adjacent circular ridge so that the minimum axial radius of the internal surface of the tubular member never decreases below the radius of the proximal end of each circular ridge; a collar of fixed diameter; and a rim of fixed diameter equal to the diameter of the collar; characterized by each of the circular ridges of the adjustable portion being operably coupled to one or more adjacent circular ridges of the plurality of circular ridges by a flexible material interconnecting adjacent circular ridges wherein each circular ridge includes a fold made by an excess of a small portion of the flexible material, the fold configured to collapse inward between adjacent circular ridges to facilitate partial insertion of one circular ridge into an adjacent circular ridge during retraction of the adjustable portion. a channel configured to facilitate passage of surgical instruments through the elongated tubular member; an adjustable portion configured to facilitate axial extension or axial retraction of the elongated tubular member, wherein the adjustable portion is defined by a plurality of adjacent extendable and retractable circular ridges centered along the longitudinal axis of the elongated tubular member, each of the circular ridges including a proximal end and a distal end, wherein the radius of the proximal end is less than the radius of the distal end to create a tapering effect along an external surface between adjacent ridges to allow for the proximal end to be partially inserted into the proximally adjacent circular ridge so that the minimum axial radius of the internal surface of the tubular member never decreases below the radius of the proximal end of each circular ridge; a collar of fixed diameter; and a rim of fixed diameter equal to the diameter of the collar; characterized by each of the circular ridges of the adjustable portion being operably coupled to one or more adjacent circular ridges of the plurality of circular ridges by a flexible material interconnecting adjacent circular ridges wherein each circular ridge includes a fold made by an excess of a small portion of the flexible material, the fold configured to collapse inward between adjacent circular ridges to facilitate partial insertion of one circular ridge into an adjacent circular ridge during retraction of the adjustable portion.