Vacuum insulation provides superior heat retention--your beverage stays hot or cold for hours. A special manufacturing technique was used to make the body ultra-lightweight and compact. Zojirushi flip-open lids are designed to release and hold, then flip open. This 2-step lid release allows condensation on the lid gasket to fall back into the mug instead of splattering. Lid completely disassembles for easy and thorough cleaning. Air vent on the mouthpiece allows beverages to flow out smoothly, without gushing or overflowing. Safety lock prevents the lid from opening accidentally. Nonstick coated interior makes cleaning easy. All surfaces that come into contact with your beverage, including the lid and 18/8 stainless steel interior, are BPA-free. Zojirushi America Corporation warrants only the thermal insulation of certain vacuum insulated products against defects for a period of five years from the date of original retail purchase. Product must be used within the US and Canada. Vacuum means the air between the outer and inner layers of stainless steel has been removed to create a vacuum insulation. It blocks heat from transferring through air (conduction). Zojirushi vacuum insulation also features a copper or aluminium layer tightly wrapped around the outside of the inner stainless steel layer. This copper or aluminium layer reflects heat (radiation), further minimising the temperature change of your drink. Lastly, heat is blocked from escaping through the opening (convection) with a tightly closed lid. Zojirushi is dedicated to offering a new generation of products that exemplify ease, affluence and style in its three main business areas: Cooking appliances, food and beverage preservation and amenities for both home and industry.