Missing or worn out pump parts can reduce your pump's suction and overall performance. To help keep your breast pump working as it should, replace your membranes and valves if you notice a tear, crack or stretching, or a decrease in your pump’s performance. Depending on how frequently you pump will determine how often you need to change your membranes and valves. If you pump on a daily basis, you will want to change your parts every 60 to 90 days. These replacement membranes and valves work with all Evenflo Feeding pumps, including the hospital strength Advanced Double Electric Breast Pump, Advanced Single Electric Breast Pump and Advanced Manual Breast Pump. Replacement membranes and valves are 100percent free of BPA, polycarbonates, PVC and phthalates and are made of FDA-approved food grade material. Gender: unisex.