In addition to standard design FNL flanged housings, variants are also available. Variants include housings with centring recesses and grease escape holes.
FNL flanged housings can be supplied with a machined recess, which can be used to centre the housing on a shoulder. With this arrangement, the attachment bolts are not subjected to shear forces. The shoulder can be provided either by machining the wall or by attaching a guide ring to the wall.