The Cummins part number 3801261 is a Main Bearing Set, specifically a 0.010 inch (or 0.25mm) oversize set designed to support the crankshaft and reduce friction within heavy-duty Cummins engines like the NTA855 and N14. These bearings are essential for proper crankshaft alignment, support, and lubrication, preventing wear and overheating to ensure engine longevity and optimal performance.