Housing made out of steel, inner square section made out of steel tube for mounting "plug-in" lever arms on one or both sides. The inserted part should be at least three times longer than the clearance "C". Up to type DR-S 18 the lever arms can be mounted by one through-bolt and the levers are then fixed by frictional force at any position within 360°. Both ways of fixation are particularly well suited for motions at the plus or minus angular range (no alternating motions across the neutral axis = play). All metal parts are paint-finished.