For 30l-40l backpack: length(11.8"-14.6"), width(5.9"-7.9"), height(18.5"-21.7"). fit range: 1800 - 2500 cubic inches.extremely durable: made of 190t nylon fabric, wear-resisting and durable. It can resist water of 2000mpa hydraulic pressure rate.dual-layer construction: external layer adopts rip-resistant nylon to protect backpack from scratch, and internal layer adopts waterproof coating process to protect your backpack and belongings from rain, water, snow, dust ,mud, and sand.Elastic compact design: it is able to adjust the size according to different backpacks, seamless, lightweight and portable convenient.multiple use: perfect for traveling, riding, climbing, hiking, cycling and other outdoor activities.