ENJOY LESS MESS & LESS STRESS: The uniquely designed straw has a spill-proof valve that opens when your child drinks, and closes automatically in between sips CLEAN UP QUICKLY: Opens for thorough cleaning; top-rack dishwasher-safe CHILL OUT: Vacuum-insulated stainless steel keeps drinks cold up to 13 hours SIP ON THE GO: The unique design allows for easy one-handed drinking 12 oz. size Cute penguin 🐧 design.