The inner tube 40 and the housing 20 are preferably made from a thermoplastic material, such as polyethylene or polypropylene, The housing 20 is sufficiently flexible and the tolerance between the flange 52 and the annular lips 33 and 35 are so designed that when the inner tube 40 is slidably removed from the housing 20, the flange 52 snaps over the lower annular lip 35 and is temporarily retained