A position-variable face-side clamping of a ring body between bearing legs with a screw bolt is to permit a central mounting of the screw bolt at reasonable cost. It must be possible to use especially profiled screw bolts for eccentric positions. For this purpose, the ring body and/or the bearing legs are provided with one oblong hole respectively which, on its longitudinal sides, has, in each case, at least two axially aligned, mutually opposite guide webs. In the case of oblong holes with only two guide webs on each longitudinal side, a centric mounting is possible by using a bolt with a cylindrical circumferential surface which can be received between the two guide webs. Eccentric offsets are permitted by the use of special formed bolts which have guide grooves assigned to the guide webs.