an exterior rearview mirror assembly for a vehicle includes an extendable mirror for improved rearward viewing . the mirror assembly includes a mirror housing , a mirror disposed in the mirror housing , and a structure to allow extension of the mirror between an inboard position and an outboard position . the mirror can include a post disposed in a mirror shell extending along a longitudinal axis offset from a central axis of the mirror . the structure for rotating the mirror can include a pivot part having a shaft disposed in an aperture in the mirror shell which is disposed along the longitudinal axis . the structure for extending the mirror can include a groove in the mirror housing in which the mirror frame is slidably disposed . the frame may be slid relative to the mirror housing from the inboard position to the outboard position .