HOW TO DRINK WATER WITH FREE FLOW: Please notic that the bite valve is the "bite and suck valve". Firstly, pull the valve in the "on" position. Then put it in the mouth, bite the groove gently with your teeth, sucking the valve at the same time. It will pop open and fluid flows freely. VERSATILITY : The water pack is your perfect choice for cycling, camping, running,music festival, rave , kayaking. A decent Holiday Gift for families and friends who love outdoor sports.If KUYOU hydration pack did not meet your expectations or if you need a replacement, please do not hesitate to contact us . PROFESSIONAL 2L HYDRATION BLADDER: The mouthpiece has been upgraded to an easy ON/OFF push valve designed and 135 degrees rotatable mouthpiece to help stop leakagea and easy drinking.You only pull up on the drinking mouthpiece, gently bite the mouthpiece with your front teeth to have a sip and start drinking, push back to stop water flow It conveniently quick to have a drink in cycling,hiking, camping. COMFORTABLE & RELIABLE: Designed with body mapping technology for efficient ventilation and lightweight comfort.Shoulders, chest, and waist,3 straps are all adjustable for reducing bounce,You'll never lose our balance because of the water load,Soft air mesh back speeds up air-flow and makes your back cool. KEEP COLDING: Hydration pack have thick insulated layer ,the insulated bladder compartment keeps your liquid cool or hot for up to 4 hours.alone bladder pocket that is to improve the insulation effect and achieve the separation of dry and wet. COMPACT& LIGHTWEIGHT : Lightweight and Durable Materials,KUYOU Hydration packs are designed specifically for road cycling /running/ Hiking ,So that's Compact and low-profile so they feel light and stable on your back and won’t create a ton of wind resistance ,keep your body functioning at peak performance whether you're training for a marathon or cycling.