[Adjustable Size & FUNCTIONAL] Hydration Backpack have fully adjustable shoulder,chest straps and waist adjuster,which helps you easily adjust water backpack size to fit your torso,Teenagers/kids with 27" up to adults (men and women) with 40" chest size,the waist 21"to 33".[Lightweight&Compact Water Backpack]Hydration Backpack is made of comfortable and waterproof nylon fabric,compact design your feeling is lightwight and stable without any wind resistance when you use it,The hydration pack's bottom also equipped invisible helmet holder pocket ,the shoulder strap is with clip fix bladder.[Insulated Hydration ]This hiking daypack has an insulation compartment which can hold a 2L Hydration bladder and your drink can be kept cool up to 4 hours in running,cycling biking,hiking,the cycling backpack is equipped with inner bladder fastener will reduce the bladder's bouncing during movement.[ hydration bladder 70 Ounce-2 Liter]Included 2L leakproof and stability hydration bladder,complete with soft high flow bite mouthpiece with easily accessible on/off,valve ,test report will be sent to your e-mail.the size of water bladder is perfect offer a nice balance of reasonable weight and bulk while providing a sufficient quantity of water.[Perfect gear for outdoor Activities]The hydration pack is perfect gear for cycling, camping, running,music festival, rave , kayaking,short trip, walking, mountaineering and ultralight hiking,Best holiday Gift for families and friends who love outdoor sports.