The 5x10x4 Ceramic Metal Bearing (MR105ZZC) is a high quality steel/chrome bearing with metal shields and silicone nitride ceramic balls (Si3N4). These bearings have been tested and proven by many racers.
5x10x4 Halo ceramic bearing by Avid Racing Concepts is the standard bearing for 1/8th nitro clutches. A ceramic can spin at higher rpms with less drag and the life of the bearing is far greater than a steel bearing but in our industry we suggest that you maintain them with oil or grease every half-gallon to a gallon for the longest life possible. Another benefit to ceramics is the weight difference in the balls allowing for less rotating mass.