Replacement nylon gasket for the most common size sausage stuffer.  Fits many brands that are 7, 9, 10, 15 liter and more.  Measure the diameter of your tank.  It should be approx 5 1/4" diameter.

The piston slips into the groove on the round plunger. The gasket is necessary to prevent meat from escaping back up the cylinder wall when stuffing sausage. 

Always lubricate your tank prior to each use with food grade silicone spray, olive oil, vegetable oil etc.