This item is highlighted as # 21 on the product illustration at the bottom center.

View a picture of the Comet MC 20/20 diaphragm pump this item goes with by clicking the thumbnail on the left.

This plug from Comet Pumps is part # 3202.0214.00 and is a replacement item that goes with the MC Series diaphragm pumps that include the MC20 / 20 and MC25 models.