The best Ceramic Ball bearings on the planet. ACER Racing's Ceramic Nitride Pro Series ceramic bearings use diamond polished Silicon Nitride balls which are the hardest and most durable ceramic balls available. We add our 100% synthetic SIN oil (or synthetic ACERGoo for certain bearings such as clutch bearings), high performance HSR inner cage for lower heat, low noise and stability at higher RPM's. Our bearings have proprietary tolerances for smooth low friction performance and sealed on both sides with no contact seals. We are the pioneers of Ceramic Bearing technology: Do not accept any imitations, Choose only ACER Racing, the racer's choice since 1989.