Patagonia and Critical Mass are not two words I usually associate with one another. Patagonia makes me think of warm fleece jackets, backpacking trips in Wyoming, or maybe rock climbing, and those fresh product catalogs which instill a wanton lust for more gear I don't need. Critical Mass? I think of bikes outnumbering cars, San Francisco, urban street riding, getting cut off by buses on Nicollet Mall. Well, Patagonia has done their homework on their Critical Mass messenger bag, that much is obvious. Like most Patagonia products I've used, construction is burly, in this case, Ballistics 1050-denier nylon, lined with packcloth for extra-durability and high water resistance. Initially, I was concerned with the lack of internal pockets. I like having a cavernous bag, AND secure pockets. This has been less of a concern, the more I use the bag. The internal zip pocket against your back for larger items/documents/cds, along with the pocket on the flap for smaller stuff works great, and has proven more than adequate. Also, the way the bag tapers at the opening allows the flap to cover it more securely. I seldom use the snap closure so I appreciate this feature. The velcro used on the flap seems to have an extra-snaggle tooth quality. There is a mesh pocket on the side of the bag. It's a great spot for my helmet light battery, but removing the battery is difficult; I can barely fit my hand into the pocket. I would suggest changing the cuff to elastic, for easier access. Also, I question the claim in the Patagonia catalog, that the bag can be worn over either shoulder. Certainly it can, but to take advantage of the quick-cam buckle for rapid adjustments, it only works over the left shoulder. Fortunately for me, that is how I carry my bags. I realize that some riders adjust the strap to the length they want and just flip the bag over their head to remove it. But I utilize the quick-cam all the time, as load sizes shift; small load=tighten the bag to my back, larger load-(BEER!)=loosen it up. There's an attachment in the center of the bag for a blinky light, and a nice reflective strip runs along the outer flap. At any rate, this is an excellent bag; well thought-out, sturdy, and comfortable. Obviously, many "outdoor" manufacturers, and clothing houses (J.Crew, Banana Republic, etc.) have jumped on the mess. bag bandwagon recently. Most of these attempts suck-and in no way am I lumping Patagonia in with these brands, simply an observation of the popularity of this bag design- Patagonia has obviously researched the needs of cyclists in creating the Critical Mass bag. Lots of people like to call this company Patagucci. Yeah, their stuff may be a bit more expensive, but you get what you pay for: years of reliable use.