Pediatrician recommended. Clinically Shown: mimics breastfeeding; significantly reduces gas and colic. BPA free. Bisphenol-A free. Phthalate free. Pre-sterilized disposable liners keep air out for more comfortable feeding. Most like mother. Playtex Drop-Ins Disposable Liners Are: pre-sterilized for a clean bottle anytime; 100% leak-proof guarantee; pre-formed for easy one-handed assembly and clean-up. Expands to 10 oz for easier bottle preparation. Generations of moms have trusted Playtex Drop-Ins System with their babies, and it continues to be the No. 1 selling bottle system (Based on sales volume). Two recent clinical studies confirm that the Playtex Drop-Ins System provides significant colic reduction and mimics the natural feeding patterns of breastfeeding: Clinically Shown Reduces Gas and Colic: In a clinical study, 8 out of 10 mothers indicated that their babies showed fewer signs of gas, colic and other feeding discomforts. Clinically Shown to Support Baby's Own Natural Feeding Pattern and Support Breastfeeding: Baby sucks and swallows in a coordinated rhythm that is similar to how they feed from the breast. Baby breathes more naturally. Baby can control the flow of milk, so he/she takes in just the right amount. The Playtex Drop-Ins System is designed to help baby switch between breast and bottle. Patented NaturaLatch Nipple: Clinically shown to mimic baby's latch-on like the breast; Slow-flow nipple designed to replicate the natural flow of the breast so baby takes in the right amount. Compatible with the Playtex Nursing Necessities breast pumps - Just pump, store and feed; Easy to store & freeze directly in the liner. Made in China.