The Avid 7x19x6 Ceramic Front Engine Bearing offers the maximum performance and reliability to almost all .21/.28 racing engines on the market at an unbeatable price. The bearing specs are Abec5, 7 G3 Si3N4 Ceramic Balls, PA66 with 30 Glass Fiber Cage, Chrome Steel 52100 Rings, and two rubber seals. A ceramic engine bearing can allow most RC engines to spin an extra 500 rpm with less drag and the life of the bearing is far greater over a steel bearing. Another benefit to ceramics is the weight difference in the balls allowing for less rotating mass (0.8g lighter then the steel ball version of this bearing).