This silicon disk membrane is the part that moves up and down when pumping and is inside the milk back flow protector (top part of shield).

 

Every so often you may want to get a new membrane for your pump. The value is vital to your pumps performance. If it's not sealing then you can lose all or some suction from your pump.

Large Membrane for Backflow Protector (Allegro and Forte)

$7.50Price