Wheat Straw Polypropylene. Composed of Reclaimed Stalks From Wheat. Less Plastic Used In The Material. Harvested Wheat Is Renewable And Sustainable. No Indication Of Extractable Gluten In Testing. 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. Meets FDA Requirements. BPA Free. Hand Wash Recommended.