Does the job..
I hate getting dirt and crap on my mouthpiece when I put my pack down, so I decided to get this. I don't know if the cover I have fit properly or not, but water still leaks from it from time to time. Its as if the cover is just snug on the mouthpiece to the point that it puts enough pressure on the bite valve to open a little. I don't know. Like I said it does the job still..