I just happened to stumble over this while deciding on a replacement for my original Timbuk2 Commute laptop bag, and thought it seemed handy to have. Little did I know at the time that I was getting a really good deal, since everyone else seems to sell these at or near MSRP.

Anyway, it's basically a lightweight opener connected to a strip of velcro. I'd guess the metal to be aircraft aluminum, and the fabric is made of the same nylon as the Timbuk2 bag straps.

Although I haven't had a chance to test it out on every bottle, I can say that it's definitely compatible with bottles of Strongbow and North Peak Siren.

One thing I do want to mention though... in the picture, you can see the opener fastened near the top of the bag strap. On both the Commute and Command straps (probably all of them), there isn't really an obvious way to keep this from sliding down to the cam buckle and going "ding, ding, ding" with every other step, unless you fasten it to the shoulder pad or improvise some way of making it "stick".