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 it's perfect for the car, park days, daycare, or home—wherever your little one goes. Easy for children to quench their thirst but won't make a mess if tipped over. The Kelso Outer Space tumbler is the perfect choice for active kids, or young ones just graduating from sippy cups who aren't ready for an open-topped tumbler yet.