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. 2-step lid release process prevents excess condensation on the stopper form being flung off while the lid opens. A special manufacturing technique was used to round the bottle opening, making it smooth and comfortable to the touch when cleaning. Bottle comes with 1-5/8" (4cm) wide mouth opening.