ColdKey™ metal straw for minimizing the amount of plastic sitting in your water, SoftSip™ silicone straw so every sip feels like a luxury, BevGuard™ technology to keep drinks cold for 24+ hours, and a cup-holder friendly base so you can enjoy 40oz of your favorite beverage, free of leaks and spills throughout your daily journey. Era Tumblers are 100% leakproof with cold beverages and iced carbonated beverages when in the locked position. A 50% ice to liquid ratio is recommended when using carbonated beverages. Not recommended to be used in the locked position with hot beverages. Using hot beverages with a straw poses a scalding risk.