1. Material different:OE standard materials 5 types, after market normally 2 types. 2. Inner diameter tolerance: fg. OE 2P8889 Φ120.675±0.037,accuracy:0.001mm; after market Φ120.65±0.037, accuracy: 0.01mm 3. Inner cycle surface net: OE have production request, the net deepth, width have standard ,after market: NO 4. Final harden technology: OE have quench, after market: NO 5. OE buyer: North America :Catepilar, Cummins etc.China: Foton Cummins, CCEC etc. Europe :Scania, DAF, Perkins, Deutz etc.