If you're a backpacker, this invaluable item will keep your mouthpiece clean and keep it from leaking from inadvertent pressure. I purchased a bladder with the system already attached and liked it so much that I refitted my older bladders with the same system. Works like a champ!
Pros: Easy to use, well made,
Cons: Can be difficult to install.
This review was written in the old system and had content requirements that are different than reviews written today.