· AUTHENTIC MEDELA REPLACEMENT PARTS: This 2-pack of Hands-free Collection Cups Membranes 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 membranes every 3-6 months, depending on your pumping frequency· MADE WITHOUT BPA: Hands-free Collection Cups Membranes are made of 100% food grade silicone· WHAT'S INCLUDED: Each pack includes two (2) Hands-free Collection Cups silicone membranes