These are replacement bearings for all Profile Racing hub shells. They also fit Madera Front and Rear hubs. 
They are sealed and self-lubricating. There are two (2) of these bearings in a Profile Racing cassette hub. The vast majority of our hubs use MFG # 6903. Fixed Hub Rear hub uses MFG #6902. Classic MTB 20mm front hubs use MFG #6805. Price is for set of two (2) bearings. Bearing seal colour subject to change without notice.