Bigger than a timbuk2 Small, smaller than a Medium. Dimensions are quite close to timbuk2’s Medium but the holding volume is a lot less (14 litres vs 22 litres; Small holds 12 litres). I was going to buy from timbuk2’s excellent online store, but USD$50 for shipping is a little too much.

I basically bought it to hold two smaller bags, which were too small to justify carrying my Fux Deluxe around for:
+ !=

Hmm.