Keep Your Gear Dry & Dust Free. Designed specifically for mounting below your bike saddle the BBB EasyPack Saddle Bag (BSB-31) will keep its contents quite dry and dust-free under most circumstances. You'll love how much you can stow in this very handy, MEDIUM-sized, storage unit. Inside the blue lined interior, you find a sweet 640 cm3 of space. Enough room to keep a spare tube, a CO2 cylinder & a few essential repair tools like tyre levers and patch kits. An elastic strap and inside pocket help with easy organization of your cargo. Rubber Seat Post Strap. On the outside the BBB EasyPack Saddle Bag (BSB-31) features a lockable waterproof zipper for extra protection from damp weather. A rubber seat post mount strap is included at the rear to provide extra stability for the bag. It also prevents damage to your seat post ... and your Lycra shorts.