Zojirushi stainless tumbler is made of high quality 18/8 stainless steel and will keep your hot beverages hot and your cold beverages refreshingly cold because of the superior heat and cold retention. Stainless steel Vacuum insulation minimizes heat transfer to keep the exterior from getting hot, and minimizes condensation when filled with ice cold beverages. Flip Lid with Safety lock prevents the lid from opening accidentally. It is a leak-proof, gasket-free, one-piece lid that is easy to clean and prevents the loss of parts. All parts are made of BPA-free plastic and stainless steel.