This is the Topeak Aero Wedge Seat Bag offering aerodynamic styling, four different sizes, with QuickClick(TM) mounting system. Our QuickClick(TM) system is built into every bag we make. It's the ultimate in convenience and security. QuickClick(TM) is Topeak's proprietary quick release mounting system that allows fast and easy tool-free mounting and removal of QuickClick(TM) equipped bags, tools, lights and accessories. A simple slide and click and the bag is secure. To remove, a simple push of a button unlocks the system for easy removal. Fast, easy and secure, the QuickClick(TM) system is the ultimate in convenience. Features: QuickClick mounting system for convenience Fitting for taillight 1000-denier Cordura Plus Weather resistant, covered zippers keep contents dry Large: 9.1" x 5.1" x 5.5" Medium: 7.5" x 3.7" x 3.9" 3M reflective strip for increased nighttime visibility