- 100% Stainless Steel - Double-wall vacuum insulation - Car cup holder friendly with a 2.75" base diameter - Includes removable silicone straw tip Our 25 oz stainless steel tumblers feature double-wall vacuum insulation to keep your drinks at the perfect temperature for hours. Bright and delightful, these tumblers will keep you reaching for a sip and hitting your hydration goals every day.