Bearings typically range in size from 10 millimeters to 30 millimeters in open, shielded or sealed designs. The 608 series bearings are the most common standardized ball bearings as of 2016. This bearing has an 8-millimeter bore, a 22-millimeter outside diameter and a 7-millimeter width.
A 10-millimeter bore bearing has an outside diameter ranging from 26 to 35 millimeters and a width ranging from 8 to 11 millimeters. A 30-millimeter bore bearing has an outside diameter ranging from 55 to 72 millimeters and a width ranging from 9 to 19 millimeters.
Ceramic and metal are commonly used to make bearings. Ceramic bearings dissipate heat and friction better than metal bearings.