608 skate bearing is type of deep groove ball bearing, 8 is the inner diameter of 8 mm. Dimensions are 22mm outer diameter, 7mm height.Normally there are 7 pcs steel balls and the diameter of the steel ball is 3.969mm. There are many type of 608 closure type such as 608 open ,608 Z,608ZZ ,608RS,6082RS bearing;For materials ,there are carbon steel, Chrome steel(GCr15), stainless steel, plastic, ceramics, etc. The cages are: nylon cages, steel cages, ceramic cages, . 608 Longboard Bearings with high precision ABEC-9,Dupont nylon cage and green color seals ,print with customer's company logo ,have widely application such as skateboard wheel ,longboard wheel .