Stainless steel vacuum insulation keeps beverages hot or cold for hours A special manufacturing technique was used to make the body ultra-lightweight and compact 2-step lid release process prevents excess condensation on the stopper form being flung off while the lid opens 1-5/8” (4cm) wide mouth opening Made of BPA-free plastic and stainless steel The Stainless Mug is ultra-lightweight and compact. The tight-fitted flip-open lid with a safety lock makes drinking from the mug easy and prevents beverages from spilling. It features a one-piece stopper with an integrated gasket and a newly designed air vent on the mouthpiece.