Set of 14 high-performance ceramic ball-bearings for XRAY T2 and T3 cars. Set of 5x10x4 bearings (10pcs) and 10x15x4 bearings (4pcs).- Si3N4 silicone nitride ceramic balls - Superior ceramic ball-bearings with decreased weight, higher RPM capabilities, increased corrosion and wear resistance - Reduced friction and vibration.