HIGH QUALITY MATERIAL:1000D CORDURA Fabric,420D PVC lining,YKK Ziper,heavy-duty construction,resistant scrapes and tears.It is lightweight and touch soft. REPLACEABLE 3L BLADDER: Includes a 0.4mm thinckness 3L/100 OZ Food grade TPU material Water Bladder Reservoir, Insulated tube, BPA free,Tastefree.Includes a wide screw cap so you can add ice cubes to keep your drink even colder. It holds enough to get you through a day of hiking,cycling, running or period after biking ADJUSTABLE SHOULD & CHEST STRAPS:Will fit chest sizes from kids and teens as small as 27" up to adults with a 50" chest. The chest straps make sure it doesn't bounce when you move; Includes a whistle buckle for emergency COMPACT DESIGN & MOLLE SYSTEM DESIGN: 19"x10"x1.5" in size; Front pockets can hold your wallet, keys, phone, towel, or small tool.Molle system can expand any extra gear which you like! INSTRUCTION OF LOCKING THE BLADDER:Step 1:Let the edge of the bladder cap out to make the backpack lock it.Step 2:Insert the small small buckle.If any question about the methord,just feel free to contact us.