The stopper, also known as a splash guard, is located over the top of a sink drain and garbage disposal unit. With a hole in the center, the stopper will allow water and food items to go into garbage disposal while keeping liquids and smaller food particles from splashing back up into the sink. It is normal for this part to wear out eventually from use, but it is important to replace if you notice garbage coming up to the surface of your sink. The stopper is a flexible rubber cover and it comes in black. Refer to the manufacturer-approved installation diagram for further instruction.