Thank you for viewing. This is a waterproof rain cover. Easy to install, just cover it completely. Reflective material on the back, sides, top, and bottom for improved safety at night. It protects backpacks and luggage tied to the rear rack of a bicycle from rain. It can also be used by covering the front basket with it. The size is approximately 50cm in height, 39cm in width, and 25cm in depth, as measured by an amateur. As shown in photos 3 and 4, there is still plenty of room even for a large high school student's backpack (50cm tall). With ample depth, it's adjustable and seems to be suitable for even larger backpacks. I bought this for my child's commute to school, but it has been used only a few times and is in very good condition. Recommended for outdoor activities, camping, mountain climbing, and fishing.