1. The present invention comprises a base fixed on a bracket formed in the housing of the mirror assembly, a pivot link installed on a concave of the middle portion of the base, an adaptor installed closely on the inner surface of the pivot link, a pivot cup installed closely on the inner surface of the adapter, a spring retainer comprising a through hole formed on the middle portion and corresponding to the opening of the base, and a connecting groove portion installed on the upper surface of a spring retainer, and a spring connected compressively between the rear surface of the middle portion of the base and the spring retainer.