Abstract: The support members for a vehicle seat include a molded plastic seat bottom support and a molded plastic seat back support. Cushion members for mounting on the supports include a cushion bun of resilient foam and a seat cover for enveloping the cushion bun. The seat cover has an opening in the underside thereof which permits insertion of the cushion bun when the cushion bun is compressed. A fastening device for mounting the cushion member includes a projecting element, preferably a headed stud, provided on the cushion member. A mating receptacle element, preferably a slot or key hole slot, is provided on the support. The projecting element and the receptacle element are positioned for mating engagement when the cushion bun is forcibly stressed to vary the spaced relation between the fastening devices provided at the respective ends of the cushion member.