World Champion ACER Racing 1/8x3/8x5/32 Ceramic Ball Bearing. This is a 1/8x3/8 ceramic ball bearing also known as a size R2 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. ACER Racing lightweight ceramic ball bearings last longer and spin faster.