The ALS55 stop cam is 55mm high and comes with an Allen bolt and T-nut for mounting in the door's C-profile. When closed, the roller door rests on stop cams. These protect the rubber profile and/or the optosensors inside from damage. The height of the cam should be selected so that the hollow chamber containing the optosensor is not compressed, but that the sealing chamber fits snugly against the floor.