These travel mugs are made of double-wall stainless steel with vacuum-insulation keeping drinks hot or cold for longer and features a non-skid foam bottom. The push-on acrylic lid has a thumb-slide closure. Tumbler: Double-walled stainless steel Lid: Acrylic Insulation: Vacuum Insulated Closure: Push-on lid with thumb-slide closure Non-skid foam base Capacity: 18 oz