1989-2018 5.9 / 6.7 Cummins Main Bearings (std)1989 2018 5. 9 6. 7 Cummins Main Bearings (std) *Sold as a complete set 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