Cycling Backpack Biking Backpack Riding Daypack Bike Rucksack Breathable Lightweight for Outdoor Sports Travelling Mountaineering Hydration Pack Unisex 6L. 1 main compartment with open pockets. there is another compartment inside, is the place for the water bag. It is also a bag in the middle in net. Inside: 1 bag outside right, you can easy to take objects during your trip. There is a large hole in the top at the back to attach the water pipe and to connect the water bag. (Note: this bag does not contain water bag, if you need a water bag, please buy separately.) The bag adopts U-type zipper design, opening big.The shoulder strap and the back of the bag containing the bulges thickenings. The breathable sponge allows the air to flow from the top and drains to the bottom and around. Adjustable straps make it perfect for every person. The belt is used to relieve stress and ensure a stable and safe ride. The chest clips help to tighten the backpack against your body，not shake violently.