Aerodynamic water-repellent lightweight saddle bag with a unique center opening for easy access to tool, tube and other essentials. Fits neatly under saddle with hook & loop straps A weatherproof seat pack made to battle the nastiest weather out there Standard model designed for road bikes and gear while the large size is more for mountain bikes and able to store a 29" tube Features water proof zippers and Topeak&';s Rail Wing system to securely attach the bag while also allowing for access Model: Weatherproof Dynawedge Mount: strap, fits 25.4 - 31.8 mm seatpost diameter Size: choose; standard, or large Material: 210 denier / 420 denier nylon / PU coating zipper Dimensions: 5.5 x 4.1 x 2" (Standard); 6.8" x 4" x 1.7" (Large) Capacity: 21 cu in (Standard); 37 cu in (Large) Weight: 45g. (Standard); 69g. (Large) Color: black