The Evernew® Water Carry/Bladder is made of low odor polyethylene to keep your water smelling fresh and resists germs and bacteria. They are designed with a tapered center for easier handling. The attached polypropylene cap is rugged and can't be lost on the trail. There is a convenient strap attached that allows you to fold it up for storage in your pack when not in use. Most of us here at Gossamer Gear carry an extra bladder just in case we need extra water. It has an antibacterial coating to keep it clean. Available in 4 sizes for all your liquid needs. It come in 0.6L, 0.9L, 1.5L, and 2.0L.