Spill-Proof Valve: Unique valve design in the straw that opens while drinking and closes automatically to prevent spills. Easy Clean: Opens for thorough cleaning; dishwasher-safe on top-rack. One-Hand Drinking: The unique design allows for easy one-handed drinking Generous Size: Set includes two 14 oz. tumblers Safe Materials: This product contains Styrene, Formaldehyde, Octamethylcyclotetrasiloxane. Convenient Pack: This 2-pack ensures you always have a clean tumbler when needed. Age Appropriate: Designed for ages 3 and up.