World Champion ACER Racing 6x10x3mm Ceramic Ball Bearing. This is a 6x10 mm ceramic ball bearing also known as a size MR106 ball bearing. Diamond polished Silicon Nitride (Si3N4) Balls, HSR cage technology and sealed on both sides. Lubricated with lightweight and 100% synthetic ACER Racing SIN Oil instead of thick grease for super fast and super smooth action.