World Champion ACER Racing 4x7x2.5mm Ceramic Ball Bearing.  This is a 4x7mm mm ceramic ball bearing also known as a size MR47 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.

PRICE IS FOR 2 pieces as shown in the photo.