Abstract: A brake booster operated, in particular, by a vacuum has an input member (32), into which an actuating force is introduced, and an output member (42) for emitting an increased force to a downstream subassembly, for example a master cylinder (12). Since each component of the brake booster (10) has a tolerance range, length tolerances necessarily occur along the actuating travel, and these have an undesirable influence on the characteristic of the brake booster and therefore have to be eliminated or at least reduced. In order to avoid a series of sensing disks (36) and distance disks (62) of different thickesses having to be kept ready for length compensation, it is proposed to calibrate the length of the input member (32) and/or of the output member (42) by the compressive forming of the latter to a desired length which is obtained from a comparison between an actual dimension and a desired dimension, and then to install said member in the brake booster (10).