It prevents the snow flakes from comming out of your barrel. Even on cold days.
For you sissy's, it gets a little cold.
It's the best looking chamber on the market and it helps to keep a consistant shot. It's priced right, and did I mention that it looks good? The bottom half twists with a little elbow grease so It will fit on any marker with just about any drop foward. Try an elbow (90*) for a cleaner fit.
I'm not shooting snow anymore so I know this works. At the chrono, my shots stay within + or - 5 FPS. What else looks as good?