The Topeak Aero Wedge Medium Bike Saddle Bag easily stores your riding essentials. It's expandable, easy to secure, and has a safety clip for attaching a light. FEATURES: Aerodynamic and expandable design Quick Release Buckle system fits all railed saddles 3M(TM) Reflective strip and safety light clip Interior compartment has a mesh pocket for smaller items Material: 1200 Denier polyester SPECS: Capacity: 0.98 - 1.31 liters Seat post diameter: Fits 27.2mm - 34.9mm Dimensions: 7.9" x 4.7" x 4.3" Weight: 4.58 oz.