Cupholder Friendly: Tapered shape with handle makes it the ideal cup -- Take Us With You wherever you go. Spill-Proof Silicone Straw Lid: Comes with a silicone straw lid to prevent spills. Double Wall Insulation: Keeps beverages hot or cold for hours. Durable: Made of premium 18/8 stainless steel. Not Intended for Hot or Carbonated Liquids : Pressure may build in the tumbler causing leaks or spills.