Nuby s Standard Neck Bottles are designed for 0 months and up. Made of durable break-resistant plastic and contains soft silicone nipple. Vari-Flo™ valve allows child to control flow rate. Top rack dishwasher safe & microwave steam sterilizer safe. An anti-colic nipples designed into the nipple helping to prevent ingestion of air by baby which may cause colic. Anti-colic air system which contains no leaks and mess.