A memory device, for a rail longitudinal guide for a motor vehicle seat, comprising two longitudinal guide rails displaceable towards each other, for the setting of the longitudinal seat position, a first memory module, which may be displaced along one of the two guide rails to set a memory position, a locking device for locking a set memory position, a second memory module, arranged on the second of the guide rails and a stop which, on reaching a relative position of the two guide rail corresponding to one of the memory positions, engages with a counter stop on the first memory module. The second memory module comprises a base body made from plastic, by which the latter is fixed to the second guide rail.