When I take my pack off for breaks, I assume like most I just dump my bag at the base of a tree. Using a hydration kit in my bag I was afraid of the mouthpiece getting contaminated with dirt, leaves, and other junk. With this device, there's no problem. It installs in just a few seconds and keeps the bite valve contamination free. The big tab on the cover makes it easy enough pull it off with your teeth when you need a drink, letting you use your hand but of course, that somewhat defeats the purpose of the valve.
"Needs to be improved so it works with one hand"
It covers the bite valve, if you have a new one. The older bite valves are too tall for this cover. But it takes 2 hands to open and close it, and it is hard to close. It does keep the bite valve from being accidentally pressed open, like when you lay your pack down on top of the valve.