Zojirushi’s Stainless Mug has a stainless steel vacuum insulation that keeps beverages hot or cold for hours! A new compact lid design has fewer parts for easy cleaning . A new 2-step method for disassembly and reassembly of lid ensures no accidental leaks, and helps prevent the loss of parts. It features an easy-to-clean nonstick interior. A special manufacturing technique was used to make the body ultra-lightweight and compact. Removable plastic mouth ring on the sipping area for a more comfortable drinking experience. 1-1/2 inch (4cm) wide mouth opening . Made of BPA-free plastic and stainless steel.