A foldable rearview mirror assembly for a vehicle is disclosed. The assembly comprises: a mounting bracket mountable to a vehicle, the mounting bracket having a base with detent features disposed on a detent circle on the base; a mirror head frame rotatably mounted to the mirror base for rotation about a mirror head axis, the frame having detent features to match the detent features of the base, the detent features of the base and the frame forming a detent system, the detent system having at least a drive position. The frame is shaped to provide an aperture to receive either of: a manual fold insert; or a power fold mechanism having a clutch mechanism, the aperture at least partially inboard in a radial direction with respect to the detent features on the frame whereby at least the clutch mechanism of the power fold mechanism can be accommodated to operate on a smaller radius than that of the detent features.