It works exactly like it is supposed to. As far as it being a little difficult to install think about it this way. The easier it is to get on, the easier it is to come off when you don't want it to. To get it on heat up the end of the bite valve in really hot water and put the hydrolock in the freezer. That will make it fit on there a little easier. Also instead of trying to twist the bite valve on you can use the cover to pull it down. Just get the valve started then bring the cover (while open) as far up as you can. Squeeze the bottom of the cover around the valve and pull down.