Medela Extra Membranes - part of Medela’s Authentic Spare Parts collection, you can now have extra membranes on hand for pumping when you need them most. Works with Medela Pump In Style® Advanced, Swing®, and Harmony® breast pumps. All parts that come into contact with breast milk are not made with BPA. Quality and performance you can trust. Authentic Medela Spare Parts are made with the quality materials and workmanship you expect and trust, only from Medela. Non-Medela spare parts can vary significantly in terms of product design, materials, and workmanship; all of which may affect the performance of your Medela breast pump. Medela Extra Membranes set comes with six membranes.