polyester. DURABLE & WATER RESISTANT - Make of high quality polyester, this bag is designed with water resistant and heat preservation effect, effectively block rain water from entering the bag quickly. but also solid and sturdy. Protective padding, provide a cushion to reduce shock when riding on uneven road. Insulated lining to keep your cold drink or food warm for hours.. LARGE COMPATIBILITY & BIG SPACE - Product Size: 38 x 15.5 x 16 cm / 15 x 6.1 x 6.3 inch, it has a main pocket of over 10L capacity and several spacious compartments, can be used to storage maps, groceries, food, tablet, chargers, smart phones, wallet, bike pump, repair tools, hot or cold drinks, and inside pockets for other small things. Solve the troubles of long outdoor riding.. HUMANIZATION DESIGN & SAFETY RIDING - Large reflective elements on both sides of the bag keeps your night ride . Open-top rear pocket with elastic cord keeps your water bottle in place. Front and bottom velcro straps ensure stability, the bag doesn't move around even if you ride on a bumpy or rocky road, and fit most mountain, road and commuter bike.. EASY TO INSTALL & MULTIFUNCTIONAL USE - Adjustable straps for quick installation and removal, fits most of road or mountain bikes' racks. The 2 long straps going across the rack as well as 2 fixed buckle, it's fastened securely to the rack and doesn't shift. It can be a bike rack bag, a handbag with built-in carrying handle or a messenger bag with a included shoulder strap.. GUARANTEE - Your complete satisfaction is our biggest goal. If you're not happy with your purchased product, let us know and we'll provide a replacement or refund. All our packages are shipped with tracking information to ensure the in time delivery. And if any problem with your orders or items, please don't hesitate to us.