Let's keep it simple: these tumblers don't leak. The silicone sipper spout design has a built-in valve that stops water from flowing when no one is drinking: 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. Two tumblers and a bonus sipper are included in the set—the 12-ounce stainless steel tumbler has vacuum insulation, which keeps drinks cold and eliminates water rings from condensation, and the 15-ounce plastic tumbler is lightweight and easy to carry. They're both durable, reusable, and completely BPA free, and you can even disassemble the lids and spouts for cleaning (these pieces are top-rack dishwasher safe). The plastic tumbler is dishwasher safe as well, though the stainless tumbler should be hand washed to preserve the vacuum seal, and we recommend hand washing both to keep the artwork bold and bright. Don't put them in the microwave—these tumblers are made for cold drinks and help your kid stay refreshed and hydrated with no leaks or spills!