130 is generally continuous because it is desirable in various embodiments to at least partially invert the distal portion 130 d and because it is undesirable to invert the proximal portion 130 p various measures may be taken to ensure that the free distal portion 130 df more readily inverts than the free proximal portion 130 dp for example in some embodiments the free distal portion 130 df may be made of thinner material than the free proximal portion 130 dp in some embodiments the free proximal portion 130 pf may be reinforced for example with a plurality of longitudinal reinforcement members 140 along the free proximal portion 130 pf for instance as shown in fig2 which is a schematic end view from the proximal end of portion of a device similar in construction and orientation to that of fig1 b the longitudinal reinforcement members 140 may be provided on an exterior surface as shown interior surface or within a wall of the free proximal portion 130 pf while four longitudinal reinforcement members 140 are shown in fig2 more or less longitudinal reinforcement members may be employed in various other embodiments in some embodiments the free distal portion 130 df may be in the form of a discontinuous piece of material for example fig3 shows a schematic end view from the distal end of portion of a device similar in construction and orientation to that of fig1 b except that a plurality of specifically four substantially pie shaped apertures have been formed in the free distal portion 130 df such that the free distal portion 130 df comprises a plurality of specifically four thin elongated members by cutting a substantial amount of material out.