World Champion ACER Racing 3x8x3mm Ceramic Ball Bearings. This is a 3x8mm ceramic ball bearing also known as a size MR83 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.