PERFECT SET - The order Include an 2L bladder & a Hydration Pack. The weight is very light, backpack and 2L bladder add up to 0.79 pounds. Use more convenient, effort. Exterior zipper pockets on sides help you to stash your essentials such as: keys, smartphone , iPad or wallet. WILL FIT YOU PERFECTLY: Adjustable shoulder/chest /waist straps. The Shoulder/chest /waist straps makes sure it doesn't bounce when you move. The straps is made of strong nylon material, Wearable,durable . Suitable for accommodating 1.5 L and 2 L of the water bladder. WATER RESISTANT AND DURABLE: The main compartment is covered with Nylon material which serves two functions. 1. It is water resistant so your belongings stay dry in light/medium rain. It is also durable reduces wear and tear so your pack lasts longer. How to drink water: Firstly, turn on the water outlet valve switch. Then bite the mouthpiece and start sucking water at the same time. Remember to bite the mouthpiece to make it slightly deformed and form a water outlet, then start sucking, and thus you can draw water. ● Professional military 2L Hydration Bladder,Eco-friendly material. Best for hydration pack. Thick bladder material is pressure-tolerant and wear-proof, Not leaking. If for any reason the Hydration Backpack doesn't meet your standards, just send it back for a replacement .