Flexible TPU constructed, BPA free for safe use during outdoor running, hiking, marathon, cycle and climbing. Made of premium food grade TPU material. Reusable, BPA-free and safe to use. Soft bite mouthpiece and easily drink water flow per sip. A dust cover helps to keep the mouth piece of the water reservoir clean. Leakproof sealing edge makes sure the pressure tolerant and leak proof features. Optimum Temperature is from -20℃ to 50℃, portable to store hot/cold water during outdoors activities. Can be folded into a very small size, and placed in your backpack. Suitable for riding, running, cycle, camping, hiking, mountaineering, outing or excursions etc.