I replaced the standard bell push with a new doorbell camera and had to move the doorbell in the process. the gate where the old cell was. This little plug closes the hole very nicely. I only needed one, but I understand why it doesn't make sense for a manufacturer/seller to sell them separately. It's rubber, not plastic, and conforms to the hole by curving around the outside corner. The fit is snug and I just slipped it on with no problem.