These are the little feet on the bottom of your machine. The originals are probably worn out. They usually are.
Carefully lay your machine on it’s back and inspect the rubber feet. These are the cushions between your machine and the table. If they’re not perfect… replace them. Be sure to scrape all the “old feet” out of the pocket before installing the new feet. This will become clear after you remove the screws which hold the feet onto machine.
Your machine has four of these feet.