10L - Dimension of 18.50 7.68 6.3 inch (L x W x H), large enough to store bike tools, bike tire pump, cable lock, clothes, power bank, towels, water bottles, maps, food, etc. This under seat storage bag includes a 10L main compartment, with 3 inner mesh pocket, help to get your essentials well organized. The top elastic drawstring can also help you tie a lot of items,like bike pump, umbrella, clothes,etc.. & Material - The bike rack bag is made of PU and EVA material, which is water resistant, durable and lightweight, easy to clean. Water-resistant material with & a fully waterproof double zipper to help you keep your belongings dry, it also comes with a rain cover, so do not worry about cycling on rainy day. (The waterproof zipper may require a little effort to pull, and requires a little attention during use).Reflective Strip & Side Water Bottle Bag - The reflective webbing and LOGO design increases nighttime visibility and the hanger on the strip can hold a taillight which can also enhance cycling at night or in low light situations. Side water bottle bag, it is convenient for you to drink water at any time during the ride.(Remember to tighten the shrink cord when you put the kettle back).Tool Free Installation - This bicycle rear seat bag come with 3 adjustable velcro straps, make it easy to be installed and unloaded in seconds, secure your Bag for maximum stability & security. This Bag does not move, shift or budge easily, helps you tie tight without getting caught in the wheel. Suitable for most bicycle racks, such as mountain bike, road bike, electric bikes.Multifunctional Bike Accessories - You can use it as a shoulder bag or handbag depending on the occasion. When off the road, you can use it at work or school. This bike luggage bag comes with a handle and adjustable shoulder strap, rack pannier bag is not only used for bicycle cycling but also can be used as a handbag, mountain climbing bag and shoulder bag for travel, camping, picnic, ski and more occasions