Does this mount at factory rocker points or does it require drilling?

This mirror mounts at factory mounting points — no drilling required. Bolt-on installation uses existing holes on your truck's door.

How stable is the mirror at highway speeds when fully extended?

The hard panel construction resists vibration and flex on the highway. Articulation is smooth and the mirror stays locked in position once you swing it out.

Will the mirror interfere with the bed when I swing it in?

Manual mirrors fold tight against the door — no bed interference. Range of motion is designed around typical truck proportions, but always do a test swing before towing a load.