don't go by the picture
Just so you are aware, the picture above is incorrect. The Ultra Sil Stuff Sack does not have a roll top closure but rather a draw cord with a standard small cordlock. In actuality, it looks and feels very similar to the stuff sack that the Therm-a-Rest ProLite 4 sleeping pad comes with.
Regardless, it's a pretty handy stuff sack. It's very lightweight and it's waterproof - two important characteristics in the backcountry. There is a handle on the bottom (closed) end which is handy for carrying it and it seems pretty durable. I keep my sleeping back in mine and it works perfectly.