Zojirushi's Proprietary Double-Wall Stainless Steel Vacuum Insulations keeps Beverages hot ot cold for hours Leak-Proof Lid with Safety Lock keeps beverage safely locked inside by preventing the lid from opening accidentally, when used according to the instruction Manual Clean and Convenient Flip-lid design makes taking a sip easy and keeps sip spout clean when closed Fits in Most Car Cup Holders (7.5 cm) diameter accomodates most car cup holders Easy-to-clean nonstick coated interior resists odor and stain