ZenErgy Bamboo Stainless Steel 16-Ounce Insulated Travel Mug Tumbler QUALITY: real bamboo and stainless steel combine to create the best looking, best feeling travel mug on the market. Natural bamboo grains make each ZenErgy mug unique. ECO-FRIENDLY: the ZenErgy tumbler is made with naturally renewable bamboo, a plant that can grow 3 feet per day. SMART: 100% BPA-free, the ZenErgy travel mug is designed to fit in most car cupholders and single-serve brewers. EFFICIENT: double-walled structure keeps your drink hot or cold for hours with minimal heat transfer to your hand. EASY: slide-locking lid keeps your beverage where it belongs. Wide mouth opening makes cleaning a breeze.