Ceramic Lightning Performance RC Engine bearing kits have a special heavy duty, steel retainer that is designed to withstand higher nitro content. Ceramic hybrids are lighter, capable of achieving higher RPM’s and sustaining higher operating temperatures than traditional bearings. Whenever using a ceramic hybrid bearing in an RC Engine, we suggest leaving both seals on for the front bearing and one seal facing the inside of the motor on the rear bearing. This protects the RC engine from possible bearing failure. When selecting your Engine Bearing kit please check to be sure you are getting the proper sized bearings for your engine or contact your Boca Bearing Sales rep for details.