SKS's Race Bag fastens to your saddle's rails and quickly detaches with a twist. Plenty of sizes ensure you can get one to fit your needs. A separate compartment for a multi-tool keeps your tube safe. And, the reflective accents add visibility in low-light situations.
X-Small: 110 x 77 x 86mm
Small: 110 x 90 x 110mm
Medium: 110 x 90 x 110 + 40mm extension