Product details:

ACL H-Series Duraglide bearings feature a tri-metal design. Fits S/B Chevy 350/400 with Large Journal crankshafts (2.100 inch). Use H-series bearings with crankshafts that have oversize fillets and where engines run in the medium to high RPM range. H-Series bearings should be used if contact patterns obtained with P-series parts are too narrow. Contact pattern should ideally cover 2/3 to 3/4 of the bearing surface. If you aren't sure which type of performance bearing to start with, the H-Series will be your best choice.