Topeak Mondo Pack with Fixer F25 with Extendable Back Pocket, 12.6 x 5.1 x 6.3-Inch (X-Large) large dual access main compartment for lightweight jacket, inner tubes, tools, etc. Safety light mount for extra safety after dark QuickClick mounting system for fast, easy on/ off and swapping between bikes Zipper docks and fabric pulls eliminate rattles QuickClick w/Seatpost Strap