preferably be of a depth substantially equal to the thickness of the flange as will be best appreciated from fig4 the diameter of the base 28 is such so as to in the final assembly align the upwardly directed peripheral lip 38 with the inclined annular wall 24 toward the bottom or wider periphery thereof whereby upon an introduction of the spout tube 26 into seated engagement within the cap opening 20 the peripheral lip 38 of the base 28 will engage the annular wall 24 and inwardly flex into positive sealing engagement therewith completely about the periphery of the base 28 when mounted in this manner physical non destructive disassembly is not possible further the development of a pressure differential between the interior of the cartridge and the exterior thereof would rather than encourage leakage between the spout and cap merely enhance the seal therebetween for example should internal pressure within the cartridge body be greater than ambient pressure the increased pressure bearing against the enlarged inner planar surface 32 of the spout base 28 will increase the sealing pressure of the flexed peripheral lip 38 with the inclined wall 24 by the same token should an internal low pressure develop within the cartridge body and in the event such an internal pressure differential tends to cause an inward migration of air or moisture about the spout tube between the tube and the hole flange 22 and along the upper surface 30 of the spout base 28 the air and or moisture will be trapped within the chamber defined by the peripheral groove 36 any increase in pressure within this groove defined chamber will bear outwardly.