An assembly set for assembling an external rearview system for a motor vehicle is provided. The external rearview system when assembled may include a base assembly provided for arrangement on the motor vehicle, and a head assembly attached to the base assembly. The assembly set may include (i) a first head assembly comprising a first rearview device comprising at least one reflective element in form of a mirror glass, and (ii) a second head assembly with at least one component of a camera monitor system. The head assembly may be configured to be detachable and is selected to be the first or second head assembly, with the first and second head assembly being exchangeable with each other.