Hybrid construction: 1 ceramic ball, 6 precision steel balls Extra-hard ceramic ball pulverizes dirt, cleans the bearing Reduced friction due to thermodynamic cooling Durability of a steel bearing, speed of a ceramic Set of 8 bearings and 4 spacers Bearing Size: 8mm x 22mm x 7mm (608) - Nylon Shield - Hybrid Ball Bearing - SET OF 8 BEARINGS - This combination of Ceramic & Titanium Coated balls allows for one of the lowest friction ratios possible. Lower friction means cooler running and longer lubricant service life. With this bearing you get the precision of ceramic and the durability of steel balls. The Ceramic ball cleans debris and cools friction allowing for a longer lasting bearing. - Balls: 1 Ceramic, 6 Precision Steel - Ball Cage: Nylon high performance ball retainer - Seals: 2 Nylon removable shields