Wicked Koyo bearings are proudly using Japanese technology and materials - like the best quality steel available. The inner and the outer ring as well as the balls are made out of chrome steel and for the cage. the engineers used glass-fiber-reinforced polyamide. The smooth running oil used for the lubrication is the lowest viscosity of Japanese-made oil in order to reduce friction. They are ultra-fast spinning and extra-durable if maintained well. The bearings from the land of the samurai fear no comparison. BE WICKED.