Dropped my pack in the mud last weekend and the bite valve stayed completely clean under the cover. It also kept the valve from freezing on a cold morning, which I didn't expect.
Claire W.★★★★★
Honestly didn't expect much from a little cover, but after a muddy weekend in the snow my bite valve stayed clean and didn't freeze up like it usually does. It fits snug and I forget it's even there until I'm glad it is.
Madison★★★★★
Slid this over the bite valve before a snowy hike and it kept the mouthpiece clean when I dropped my pack in the slush. The cover also seemed to slow the freezing a bit, which is exactly what I needed on a cold morning.