BAG SIZE: 46*26*13CM COMFORTABLE: An incredibly comfortable padded mesh back and a highly breathable sponge lumbar pad for maximum breathability all day long. DURABLE: This 20L hiking backpack is made of high-quality tear and water-resistant material, providing extra strength and long-lasting performance with the lowest possible weight. Two-way heavy-duty SBS zippers across the backpack are convenient to use no matter which side you prefer. 20L TRAVEL CAPACITY: Suitable for day trips or hikes. A large main compartment for books and personal computer, a zippered pocket with an extra padded tablet pocket, two small zippered front pockets for mobile phone, keys and sunglasses, two side pockets to hold water bottles and umbrellas. Spacious pockets keep everything organized, such as hydration bladder, clothes, laptop and more. Thermal insulation function: the materials inside the bag have a certain thermal insulation effect. When you go outdoors, you can put the water bottle in the bag to maintain the water temperature. There is a water tube buckle on the strap, which makes it easier for you to drink water. With survival whistle