18/8 STAINLESS STEEL INSULATED: Double wall vacuum insulation design Keep your drinks hot for 9 hours and cold for 12 hours) Premium material makes it never rust, anti - perspiration, no condensation and easy to clean. This tumbler is as functional as it is stylish. With double wall vacuum insulation technology, your drinks will stay hot for 9 hours or cold for 12 hours. Plus, our premium stainless steel is rust-proof and anti-perspiration, so no more worrying about condensation or difficult clean up.