A vehicle seat bolster is adapted for attachment to a seat back, wherein the seat back has first and second sides and front and rear portions. A center portion of the seat bolster is removably attachable to the rear portion of the seat. First and second opposing arms extend from the center portion. Each arm includes a distal end which is removably attachable to the respective first and second side of the seat back such that the seat bolster provides lateral support for the seat back. The seat bolster is quickly disconnectable from the seat back for removal and installation of similar bolsters with varying load carrying capacity.

Vehicle seats are constructed with a seat cushion for supporting the lower body of a passenger and a seat back for supporting the upper body of the passenger. A side holder portion, which is filled with foam material for supporting said passenger at side portions of the upper body, is combined with a backrest portion, which also is filled with foam material for supporting said passenger on the back, such that said side holder portion is integrally and continuously formed with said backrest portion. An opening portion preferably is formed in each of the side holder portions such that said opening portion provides a hole in said side holder portion.