UPDATE: have to return to Amazon. Doesn't fit my bike (at all). I'll look at the Topeak one. Any other suggestions for a good clip-on seat bag, with a little extra room?

I wanted to get a new seat bag that was a little bigger than the Topeak wedge I've been using and I wanted one that had a quick-release attachment--tired of unstrapping the Topeak after every ride when I throw the bike onto the stand for a quick chain wipe and cleanup.

Found this for $25 and looking forward to see if it fulfills its promise.