Four-Bolt, Round Cartridge - Normal Duty Four-Bolt Normal Duty Flange Bearing Unit Application Four-Bolt Normal Duty Flange Cartridge Bearings may be found in a variety of applications, particularly agricultural equipment. Benefits using Flange Cartridge Bearing Units Flange Cartridge Bearings may be installed in equipment in cartridge form (i.e. installed within a housing/machine area) and are also suitable for surface mount installation (similar to square Flange Bearings).