Standard size XP series Rod and Main Bearings sets compatible with Chevy 327 large journal, 305 and 350 small blocks. XP-Series rod bearings feature advanced metallurgical and geometric technologies that meet extreme performance loads. They were developed for all performance applications that use forged steel aftermarket crankshafts and produce high loads for extended periods. These innovative, race-only Xtreme Performance tri-lecular bearings are proven track-tough to handle the ground-shaking power of your race engine. Built with enhanced tri-metal, these XP-Series main bearings layer copper lead construction with a nickel plate barrier and a lead/tin/copper babbit overlay over a steel backing in an adhesion process that provides superior stability and durability. Advanced control measures hit a bull's-eye, maintaining wall thickness tolerances far tighter than their competitors—an amazing +/- .0001 in.! These XP-Series bearings are narrowed for large radii crankshafts and feature enlarged, chamfered oil holes with full, 3/4, or 1/2 grooving for improved oiling. How many reasons do you need to use a specialist? XP-Series bearings deliver consistent and reliable performance with a high-load capacity, and the prognosis from the specialists is a long and happy life for your engine.