An exterior rearview mirror assembly for a motor vehicle is disclosed having a primary mirror and a spotting mirror. Both the primary mirror and the spotting mirror are secured to the same single mirror support, or backing plate. The spotting mirror is snap fit to the backing plate by having a monolithic structure which is receivable by a recess or hole in the backing plate. The recess acts as a securing device by receiving an abutment surface extending outwardly away from the monolithic structure which snaps over the backing plate and prevents the spotting mirror from moving away from the backing plate.