This adapter allows you to bolt Fatties mirror heads on to any mirror arm that has a pass through hole. Hole in arm must be 5/16". If yours has a smaller hole you will need to enlarge  it to 5/16"

This adapter allows you to bolt Fatties mirror heads on to any mirror arm that has a 5/16-24 threaded hole.

This adapter allows you to bolt Fatties mirror heads on to any mirror arm that has a 1/4-20 threaded hole.

This adapter allows you to bolt Fatties mirror heads on to any mirror arm that has a 1/4-28 threaded hole.

This adapter allows you to bolt Fatties mirror heads on to any mirror arm that has a 6mm threaded hole.