Thermal efficiency and ergonomic design. Isothermal double wall structure: Double-wall construction keeps water cold twice as long as regular sport bottles. Cap with soft push-pull tip and protective cap. CAP: Copolyester resin – taste your beverage and not your bottle. Cap can be completely removed for better cleaning and fill up. Wide-mouth opening is easy to fill with ice and water and a breeze to clean. Bottle body with easy-squeeze polyethylene.