How fast of a bicycle is most determined by the performance of it's revolving components, wheels are the main components of a bicycle. This makes it reasonable to upgrade the bearings, all the points lead to a result, Ceramic material. There are 2 main features of using Ceramic Bearings:
1. Ceramic Ball is closer to perfect round: A steel ball in Grade G25 is meant to be a high quality ball in this material, if measured by size, it's precision is 25/1,000,000 inch.
Nevertheless, a ceramic ball can be made to be in Grade G5, it's precision is much higher than the best steel ball. That's why we say Ceramic Ball is closer to perfect round.
2. Ceramic Ball is stiffer: Stiffness is very important to a ball used in a bike, it's also called "Modulus of Elasticity". A steel ball's Modulus of Elasticity is around 30,000,000Pounds/Inch, while a ceramic ball's is 47,000,000Pounds/Inch.
Both of the main features make the bearing with ceramic balls smooth, easy to maintain and fit for all conditions.
Also upgrading to ceramic bearing brings a lot of benefits over the steel counterparts: