Tundra 20oz Water Bottle (Red) Double Wall, Vacuum Sealed, Copper Lined Stainless Steel Water Bottle. With a narrow mouth and vacuum insulation, the Tundra 20oz Bottle is perfect for keeping your drinks COLD (24 hours) or HOT (12 hours) while you're on the go! The matte powder coat finish gives the Tundra a smooth sleek look. It has a copper lining, double wall made of 18/8 stainless steel, and a proprietary insulated lid. BPA free!.