Made of thick PE+EVA material, which is durable, wear-resistant, odorless, and can withstand great pressure. The water reservoir is double sealed and hemmed, and the sealing stick locks the bladder hole tightly, making it leakproof even under pressure. The soft mouthpiece with an accessible ON/OFF valve prevents leakage. The 2L hydration bladder has a large water hole, allowing you to easily fill water or add ice cubes to get cold water. It also makes cleaning the bag easier. Simply turn on the switch valve and gently bite the mouthpiece with your teeth to suck water, and lock it after drinking. When removing the sealing stick, you can easily clean the inside of the water reservoir. The TPE mouthpiece with a dust-proof cover prevents leaking when it's not in use.