Kit for automobile seat slides and related assembling method

The mounting for a seat in a motor vehicle, with a manual or motorized longitudinal adjustment of its position, has an upper rail (2) fitted to the seat and a lower rail (1) secured to the floor. Bodies (3) of different sliding characteristics are between the rails to give a high and a low friction grip. The low friction body has at least one roller (310,320) as a roller and/or ball bearing. The high friction body is a one-piece injection molded or die cast plastics component. The bodies have a zone (31) to take up the weight from the seat, and a second zone (32) to take up forces at right angles to it.