Calicle cups are made of 18/8 food grade stainless steel, also known as 304 stainless steel. They have a double-walled vacuum insulated construction with a layer of copper plating. This gives them amazing insulating properties. The non-slip base is made from food grade silicone. The lids are made of clear, shatterproof Tritan with a food-grade silicone gasket and steam release/sealing valve.All pieces are BPA and phthalate free and meet FDA standards.