The Revelate Designs Spinelock Seat Bag integrates user tested and approved features like a one-way air purge valve, rear light slots, loop and bungee deck, and an external plastic bottom with a new patented attachment system built for stability a Innovative Spinelock stability system completely eliminates side to side sway a Two mounting positions to accommodate seatpost setback and saddle adjustments a Low profile, high strength, forged aluminum clamp works in combination with precision IGUS bushings to form a quick-release pin interface making bag removal a cinch a One way, low profile, air purge valve a Carbon seatpost friendly (not compatible with carbon fiber saddle rails) a Top mounted external webbing and bungee for additional storage a A Torx-25 wrench is needed for installation. you likely already have one on your multi-tool! a The 16L Spinelock requires 8.5"/22 cm tire clearance and 6.5"/16.4 cm exposed seat post a Attachment Method: Quick Connect a Waterproof: Yes a Volume: 16 Liters a Weight: 680 g. a Color: Black