Nice and spacious, and seems bulletproof. The buckling strap feels more secure than the typical velcro. WIth the dual zipper, I can keep a large headlight battery in here and route the cable however I like (with single-zipper bags, you have to rotate the battery so the cable emerges at a corner, which can be irritating). Enough room for a couple of Clif Bars, air chuck, CO2, multitool, cell phone, and even a wadded shell--- hard to imaging needing anything more for a single-day trip, even if you're in a pocket-less jersey. The loops on the zipper pulls are perfect for a short cable lock to discourage idle browsing when I leave it parked in the city. The only potential problem is that it's large enough that it will stick out a couple of inches behind a typical saddle--- never in your way, but it might attract more attention (when the bike is parked) than a smaller bag.