Like fuji, I have the medium and the small. I could not fit shoes, pants, and a shirt in the small. I use it as a purse. I can fit a Kryptonite lock in it when need be. The medium is huge, and holds anything I need to carry. Sometimes I use my panniers instead of the timbuk2/med just so I don't have so much bulk on my back.

I recently saw their bike bags, and think I'll get an underseat bag at some point when I haven't made some other impulse buy that week!