Contain 6 sealing caps for Avent Natural Polypropylene bottles, and Nenesupply wide-neck bottles. Each cap contains 1 silicon sealing ring to prevent leaking.;Design to use with Avent Natrual Polypropylene bottles. Does NOT work with Avent Classic bottles, Avent Glass bottles or Avent VIA cups.;One piece design. Replace Avent Natrual Screw Ring, and sealing disc. Less parts to clean and easy to store.;Can be used within temperature of - 20~110C. Can be sanitized with water steam or boiling water.;Made from BPA free material. Comply with EU Commission Regulation (EU) No 10/2011 for plastic materials that intended to come into contact with food. Every batch is tested by independent labs for quality and safety.