This is the exact bite valve that came with my nathan hydration vest. Exactly this - which I unfortunately didn't know until I purchased this as a replacement for the valve that leaked when I bough my Nathan vest. Within two weeks of using it leaked like crazy and had to be left in the "off" position except when drinking. Even then it sucked in lots of air when drinking. It is made up of at least 4 different molded parts - way to complicated. What were the designers thinking? Even when it is not working it takes two hands to open and close the valve. Of course, if it didn't leak you could just leave it open. I replaced it with a camelbak valve. Save yourself some frustration - give this valve a pass.