Sea to Summit Delta InsulMug features a groundbreaking advancement in thermal insulation. Sea to Summit use an integrated molded EVA sleeve that actually insulates the liquid inside the mug, unlike double-walled mugs which only protect your hands but don’t necessarily keep your beverages hot or cold. Well designed leak-proof sipping lid has an ergonomic rolled edge and thumb grip with hang loop. Excess liquid flows back into the sipping hole because of the concave design of the lid. Features: Ultra-durable food grade Nylon 66 inner is BPA free. Fitted, ThermoSkin non-absorbing insulation sleeve.