This backpack can hold Water Bladder(not included ) BAG SIZE: 40*25*8CM Lightweight & CompactEasy to carry, can be folded into the wallet size fit into a pocket. Water Resistant materialThis lightweight hiking daypack is made of water-resistant material and zipper. Effectively prevent rainwater from wetting the phone or cash and other items in the backpack. DurableTear-resistant 30D nylon will effectively prevent branches, stones from scratching the pack, keys and other products can also be safely placed inside. All stitches are strengthened to suit long-term use. MultipurposeThis Foldable backpack provides enough space for outdoor travel, camping, hiking, day trips and shopping. Comes with a main zipper pocket, a front zipper pocket and two mesh side pockets. The main compartment provides enough storage space for day trips, hiking and shopping. It is also an ideal choice for international travel at the airport.