Shimano Line Roller Ceramic Bearings Set of 1 Ceramic Bearing GX Shield Type Line Roller is a type of bearing that combines durability, smoothness and ultra-microscope. Can be used in fresh water without oiling (not absolutely rust). Reduces line problems to the extremes. Even if the oil is used, it can reduce line problems with low viscosity oil. In addition, the salt requires oil, but the oil viscosity is lower than stainless steel bearings, reducing line issues. Can also be used for handle knobs (bearing confirmation)