1989-2018 5.9 / 6.7 Cummins H Series Coated Main BearingsCummins H Series Coated Main Bearings These H and HX Clevite bearings were developed primarily for use in NASCAR type racing but are suitable for all types of competition engines. H series bearings have a medium level of eccentricity, high crush and rod bearings have a hardened steel back and thin overlay. These bearings also have enlarged chamfers for greater crankshaft fillet clearance and are made without flash plating for better seating. The HX