The Perkins GLYH10264 is a genuine OEM main crankshaft bearing, specifically designed with a 0.25mm undersize. This bearing is crucial for the proper functioning of the crankshaft assembly in Perkins engines, ensuring smooth rotation and minimizing friction. The 0.25mm undersize indicates it is intended for crankshafts that have been reground to a smaller diameter, requiring a thicker-walled bearing to maintain correct oil clearance and extend engine life. It is compatible with a wide range of Perkins engine series, including 400, 700, 800, 900, 1000, 1100, 1200, 1500, 1700, 2200, 2500, and 2800 Series, as well as specific models like 1004-4, 1004-4T, 1006-6, and 1006-6T.