Abstract: A lightweight rearview mirror assembly for vehicles and a method for forming the same. The assembly includes a case formed from a thermoplastic material and a mirror element mounted therein. A thin, upstanding edge of the case is heated and curled into an arcuate, peripheral, retaining edge extending over the entire length of the mirror edge. The curled, arcuate edge defines therewithin a space extending between the entire thickness of the peripheral edges of the mirror and the case which allows the mirror and case to expand or contract in extreme temperatures without expelling or breaking the mirror element. Means are provided for preventing the mirror from vibrating within the case.