Todd Coxwrote a review of Stoic WPF Compression Sack on May 16, 2011
I got two red ones recently because they were cheap, then read other Todd's review. Sure enough if you get the M, then squash it flat you get a lot of compression and a shape that packs very naturally into a pelican case/saddlebag/trunk. They're not quite as versatile as a basic sack for stuff you can't squash but for anything you can flatten this is a big winner. The Medium size is pretty big already, I have to assume the orange is hugenourmous.