Several years ago I upgraded all of my water bladder systems to the CamelBak Military bladders because of their modular systems, and I like the on-off water valve. By going with modular systems I can replace parts as they break, VS replacing entire bladders. Recently my son was on a Boy Scout camping trip where his bite valve got torn and he needed a new one. I thought he should also have the cover to prevent similar instances in the future, so I bought the Hydroloc Assembly to replace the old one with. The product arrived quicker than expected, and a quick snap in, and my son was ready for his next hiking adventure! Thanks CamelBak!!!