I've got one that came with my Deep Jungle. Used it about 20 nights with a 40F topquilt. It's adequately sized (for me, probably generously sized for anybody else) and has some elastics that clip at each end of the tent to hold it in place. You might take it down near the claimed 40F if you tend to sleep very warmly. It's pretty bulky no matter how you try to roll it, but no worse than comparable CCF. I don't have any real problems with it, but it's one part of that setup that I'm constantly wishing I had a better option for. If you've got a CCF setup, I don't think there's any need to pick up the double bubble.