to the test fluid delivery tube 24 by virtue of the threads formed on the test fluid delivery tube 24 the threaded engagement between the test fluid delivery tube 24 and the rigid end caps 32 34 preferably forms a fluid tight seal between the test fluid delivery tube 24 and the rigid end caps 32 24 to allow the bladder 20 to be inflated without fluid leaking through the interface between the delivery tube 24 and the end caps 32 34 it is contemplated that a sealant may be used to strengthen the fluid tight engagement between the delivery tube 24 and the end caps 32 34 a pair of locking rings 36 38 may be used to connect the inflatable bladder 20 to the end caps 32 34 each locking ring 36 38 cooperates with one of the pair of rigid end caps 32 34 to secure the inflatable bladder 20 between the locking rings 32 34 and the end caps 36 38 the locking rings 36 38 fit over respective insertion portions 31 33 of the end caps 32 34 and may be positioned adjacent to or in abutting relation with the respective flange portion 35 37 of the end caps 32 34 the locking rings 36 38 may define an outer diameter that is flush with the outer diameter of the corresponding flange portion 35 37 furthermore the locking rings 36.