The whole shebang including the metal outer is pressed into the frame via friction. You need to make a puller. A socket the fits over the donut, and a smaller one on that butts up against the mount on the other side. Run a piece of threaded rod or a long bolt threw the bigger socket, the mount, and finally the smaller socket. Tightening will pull the mount out of the frame into the larger socket. Reverse to put in the new mounts.