Double walled Lemonavi 300ml Stainless Steel Walled Thermos Cup steel thermos cup (300ml). The outer wall is Lemonavi 300ml Stainless Steel Walled Thermos Cup steel, the inner wall is plastic. The screw on lid is leakproof and has a snap opening. The bottom of the cup is anti slip. The double walled design keeps drinks hot or cold for several hours and prevents condensation on the outside of the cup.