Disney Travel Lock cups feature a built in, spill proof, easy to clean valve system. Since the valve is built right into the lid there are no small parts to lose, and it's super easy to clean. Even better is the travel lock design - which solves the issue of sippy cup leakage on the go. No more drips in your diaper bag, purse or car. Just fill up the cup, screw on the lid, and you're good to go!