Let's keep it simple: this tumbler doesn't leak. The silicone sipper spout has a built-in valve that stops water from flowing when no one is drinking, so kids can quench their thirst without the mess if it tips over. Perfect for car rides, park days, daycare, or home. It's the ideal choice for active kids or young ones just graduating from sippy cups. This Spidey and His Amazing Friends Kelso tumbler is vacuum insulated to keep drinks cold for up to 10 hours and stop condensation from leaving water rings.