The Bird Feeder stem bag is big enough to hold a classic Nalgene bottle.  But you can fill it with whatever you like.  Now let’s all take a moment to get real.  Tan wall tires are cooler than other tires.  It’s science.  We all agree.  Now here’s a bag that can quadruple that cool factor.  Again, it’s science.  Oh, and X-PAC, Cordura snd top notch Ripstop liner mean it will hold up to lots of adventures.