Premium steel ball bearings from Primitive Skateboarding. Nylon cages for reduce weight and friction. Deep-groove design to withstand higher impact. Dust-resistant, frictionless removable shields. Lubricated with low viscosity, non-corrosive oil. Standard size 608 (8mm bore diameter x 22mm x 7mm). These bearings are Skate rated, they do not carry an Abec rating.