MATERIAL: The durable tumblers are made of plastic and stainless steel with silicone straws. Long-lasting and BPA free, the lids and plastic tumbler are top rack dishwasher safe, while the stainless steel tumbler should be hand washed. Do not microwave..SIZE: The set contains two tumblers and one additional sipper and straw. The plastic tumbler has a capacity of 15 ounces and the double-wall stainless steel tumbler has a capacity of 12 ounces..LEAK-PROOF DESIGN: Each silicone straw has a built-in valve that allows liquid to flow when drinking and prevents accidental spills when the tumbler is tipped over. The straw is also soft and comfortable for kids to drink from..AT HOME OR ON THE GO: The straw tumblers are suited for travel, since they won't leak while keeping drinks easily accessible. They're also great for drinking beverages at home without worrying about spilling on papers or electronics..LIFESTYLE: Zak Designs drinkware makes hydration a fun part of your daily routine! These Spider-Man tumblers are great for kids just graduating from sippy cups. The tumblers are fully reusable--no more disposable cups--and you can choose the material that best suits the situation.