AUTHENTIC MEDELA REPLACEMENT PARTS: This 2-pack of Hands-free Collection Cups O-rings is an authentic spare part made by Medela and designed to work with the Hands-free Collection Cups that are sold separately from a breast pump. COMPATIBILITY: Works only with the Medela Hands-free Collection Cups REPLACE REGULARLY: Medela recommends replacing your O-rings every 3-6 months, depending on your pumping frequency MADE WITHOUT BPA: Hands-free Collection Cups O-rings are made of 100% food grade silicone WHAT'S INCLUDED: Each pack includes two (2) Hands-free Collection Cups silicone O-rings