Ceramic Skateboard Bearings Size
Generally in the skateboard industry, 608zz (8x22x7mm) is the most popular and most widely used bearing. A vast majority of customers will choose this specification, while some may use other sizes as well,include 6900zz(10x22x6mm), 627zz(7x22x7mm)
The ceramic skateboard bearings are typically hybrid ceramic bearings, meaning the inner and outer rings are made of steel or chrome, but the rolling balls are made of a ceramic material. The ceramic material typically used in skate bearings is Silicon Nitride (Si3N4). Bearings made of 100% ceramic are also available, but they are typically used in electric motor applications because of their nonconductive properties.
Definition of "Ceramic"
Any of various hard, brittle, heat-resistant and corrosion-resistant materials made by shaping and then firing a nonmetallic mineral, such as clay, at a high temperature.
Here are some of the claims made by the manufacturers of ceramic bearings, but note that some of these claims were made for hybrid ceramic roll ball bearings (the same type used in skates) that are used in manufacturing equipment, so I don't know if the same claims would be made when those bearings are used in skates.
60% lighter than steel balls
Centrifugal forces are reduced
Lower vibration levels
Less heat builds up
Reduced ball skidding
Fatigue life increased
50% higher modulus of elasticity
Improved spindle rigidity
Naturally fatigue resistant
Low adhesive wear
Improved lubricant life
Superior corrosion resistance
Bearing service life is two to five times longer
Running speeds are 50% higher
Overall accuracy and quality improves. Better workpiece finish characteristics
Lower operating costs
High temperature capability
Cutting tool life is increased Ceramic bearings, hybrid, are constructed of steel inner and outer rings with ceramic (typically Si3N4) balls in place of steel.