A composition comprising a fluid handling tube and a cap configured to engage with the tube, wherein the cap comprises: a proximal terminal surface; a distal opening; an interior void; a tube insert region disposed proximal to the distal opening and comprising: two or more annular projections (334, 339) disposed on the tube insert region, and a circumference around an exterior surface of the tube insert region disposed proximal to the annular projections and defined by a sidewall; and axially oriented ribs (325A, 325B) disposed around the circumference, disposed proximal to the tube insert region, disposed distal to the proximal terminal surface, each rib comprising a distal terminus and rib distal termini define a step between the rib termini and the sidewall of the tube insert region; which tube insert region comprises an axial length and a minimum outer diameter between the annular projections, wherein a ratio of the axial length to the diameter is less than 0.62; and wherein the tube comprises: a proximal opening, a flange around the proximal opening, comprising a proximal surface, a sidewall, an interior, a cap insertion region in the interior and distal to the opening, configured to receive the tube insert region of the cap; a bottom, and characterized in that the tube further comprises two or more annular projections (140, 145) disposed in the cap insertion region; wherein, upon sealing engagement of the cap and the tube, the composition is characterized in that it comprises a pivot point disposed at a point on the flange proximal surface of the tube and disposed at a point on the step of the cap and the tube insert region of the cap is configured to permit the cap to pivot with respect to the tube at the pivot point, and the annular projections of the tube are configured to contact the annular projections of the cap when the tube and the cap are sealingly engaged. a proximal terminal surface; a distal opening; an interior void; a tube insert region disposed proximal to the distal opening and comprising: two or more annular projections (334, 339) disposed on the tube insert region, and a circumference around an exterior surface of the tube insert region disposed proximal to the annular projections and defined by a sidewall; and two or more annular projections (334, 339) disposed on the tube insert region, and a circumference around an exterior surface of the tube insert region disposed proximal to the annular projections and defined by a sidewall; and axially oriented ribs (325A, 325B) disposed around the circumference, disposed proximal to the tube insert region, disposed distal to the proximal terminal surface, each rib comprising a distal terminus and rib distal termini define a step between the rib termini and the sidewall of the tube insert region; which tube insert region comprises an axial length and a minimum outer diameter between the annular projections, wherein a ratio of the axial length to the diameter is less than 0.62; and wherein the tube comprises: a proximal opening, a flange around the proximal opening, comprising a proximal surface, a sidewall, an interior, a cap insertion region in the interior and distal to the opening, configured to receive the tube insert region of the cap; a bottom, and characterized in that the tube further comprises two or more annular projections (140, 145) disposed in the cap insertion region; a proximal opening, a flange around the proximal opening, comprising a proximal surface, a sidewall, an interior, a cap insertion region in the interior and distal to the opening, configured to receive the tube insert region of the cap; a bottom, and characterized in that the tube further comprises two or more annular projections (140, 145) disposed in the cap insertion region; wherein, upon sealing engagement of the cap and the tube, the composition is characterized in that it comprises a pivot point disposed at a point on the flange proximal surface of the tube and disposed at a point on the step of the cap and the tube insert region of the cap is configured to permit the cap to pivot with respect to the tube at the pivot point, and the annular projections of the tube are configured to contact the annular projections of the cap when the tube and the cap are sealingly engaged.