Zojirushi stainless steel Vacuum insulated mug keeps beverages hot or cold for hours with a tight fitted flip-open lid. The easy-to-clean double layer nonstick coated interior enhances durability and provides greater protection of the stainless steel against salt-containing beverages like sports drinks. The 2-step lid release process prevents excess condensation on the stopper from being flung off when the lid is opened. The lid also contains a safety lock feature to prevent the lid from accidentally opening. The air vent on the mouthpiece allows beverages to flow out smoothly, preventing any gushing or overflowing. The bottle's wide-mouth opening is 1-5/8" (4cm). a special manufacturing technique was used to make the body lightweight and compact for easy and convenient portability. All parts are made of BPA-free plastic and stainless steel.