BPA-free polyurethane film is protected by technology Slide lock opening with large opening accommodates ice cubes and easy cleaning after use Hydration Reservoir utilizes radio frequency welded seam technology on seams and exit port to ensure a strong leak proof bond Angled easy flow bite valve provides a constant flow rate TPU (Thermoplastic Polyurethane) tubing is odor free and taste free Volume markings on the front for making it easy to mix electrolytes or your favorite drink 2.0L replacement hydration reservoir