Banjo Brothers' Medium Seat Bag is perfect for carrying a tube, tire levers, patch kit, a mini tool, your wallet and some food (each sold separately). And if you're going big, it expands to haul more gear. It's made from super-tough 1680-denier nylon with a full liner and a padded top and bottom. It's got a wide-mouth opening for easy access, three interior pockets and a key clip to keep your gear organized, plus gusseted sides that keep your gear in place when the bag is open. And you've got 360 degrees of visibility with reflective accents and a tab so you can attach a taillight.
Capacity: 65-81 cubic inches
Dimensions (unexpanded): 6.75 x 4 x 3 inches