Made with double thickness material, the Flexible Peristaltic teat encourages seamless latching. The Flexible Peristaltic teat also offers a unique venting system which helps to minimise swallowed air and help reduce colic in babies. This teat opens only when your baby sucks. The harder the baby sucks, the more the teat will open and vice versa. This baby bottle teat is BPA and BPS free.