18/8 pro-grade stainless steel is used in Bottlebottle coffee tumblers to ensure pure taste. Our insulated tumblers come with a stainless straw and do a good job of insulating. The flip mouth of our tumblers may be a better alternative if you primarily want a thermal cup to drink hot coffee from. Insert the stainless steel straw if you wish to drink cool bervage to support your actions; it will provide you more experience.