The Arundel Dual seat bag is the perfect compromise between the two extremes of seat bag design. It's bigger than a coin purse sized bag that barely has enough room for a road tube, yet it's smaller than the carry-all sized bag that holds a virtual bike repair shop.
The Dual is small enough to nestle under a seat without scraping against your thigh. It has enough capacity to hold two 700C tubes and two CO2 cartridges, plus an inflator. So, why two sets of spares? Because you never know what's up the road, and it's nice to know that you're prepared. That extra tube will make the rest of your ride that much more enjoyable knowing that you won't have to use your cell phone if another flat occurs.
The double stitched Velcro straps are simple, yet secure. When the Dual is fastened to the seat rails, the end of the strap is in just the right spot to avoid tearing up your expensive cycling shorts. The Velcro has a long enough contact patch to hold the bag securely. The straps hold the bag against the seat clamp mechanism with a leather patch at the interface that protects the nylon bag from wear and prevent holes.