Aerodynamic seat bag holds tubes, tools and other repair items. Mounts with our innovative Quick Release Buckle system to fit all railed saddles. Four sizes offered to exactly fit rider&';s needs. Aerodynamic styling with traditional strap mount. Sizes: Micro - 25 cu. in. Small - 50 cu. in. Medium - 85-100 cu. in. Large 90-120 cu. in. The medium and large packs have an extra zipper which allows them to expand in size. The product weight specified is an approximate weight based on the manufacturer&';s specifications (if available) or our measurement of one or two examples. For most products, the weight will typically vary by 5% to 10%.