Stainless Steel Outer And Inner. Double Wall Construction For Insulation Of Hot Or Cold Liquids. Snap-On, Spill-Resistant Thumb-Slide Lid With Rubber Gasket. Due To Vacuum Insulation Technology, Capacity Is 18 Oz. With Lid On. Keeps Drinks Hot Or Cold Up To 6 Hours. Meets FDA Requirements. BPA Free. Hand Wash Recommended.