Let's keep it simple: this Spaceships 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 easy for children to quench their thirst but won't make a mess if the tumbler is tipped over. It's the perfect choice for active kids, or young ones just graduating from sippy cups who aren't ready for an open-topped tumbler yet. This 15-ounce travel tumbler is vacuum insulated to keep drinks cold for up to 10 hours and stop condensation from leaving water rings.