Slick Steel finish interior is corrosion resistant and repels stains Stainless steel vacuum insulation keeps beverages hot or cold for hours 2-Step lid release process prevents excess condensation on the stopper from being flung off while the lid opens Air vent on the mouth piece allows beverages to flow out smoothly, without gushing or overflowing Safety lock to prevent the lid from opening accidentally Zojirushi stainless steel 16 Ounce mug has a Vacuum insulation that keeps beverages hot or cold for hours. Easy-to-clean nonstick coated interior. Tight fitted flip-open lid keeps beverages hotter or colder than travel mugs. Safety lock to prevent the lid from opening accidentally. Lightweight design for added portability.