6903 Ceramic Ball Bearing from World Champions ACER Racing. This is a 17x30x7mm ceramic ball bearing also known as a 61903 bearing. Uses diamond polished Silicon Nitride Ceramic Balls. Price is for one 6903 ball bearing so please choose the quantity you wish to order. 

The advantages of our ceramic bearings are vast including lighter weight, lower friction and heat, greater speeds and much greater durability. Fully sealed on both sides.

This is also a direct performance upgrade for the Fulcrum R4-004 bearing