Specially designed for use with Playtex Nurser bottles. Convenient disposable liner collapses to keep air out of the milk. BPA free. What makes the Playtex nurser with drop-ins liners different? Drop-Ins Liner: As baby feeds you can see the soft liner gently collapsing to prevent air from mixing with the milk and getting into baby's tummy. This means less gas and less discomfort for baby. See how it works at www.Playtexbaby.com. Made in USA.