XD-15 ceramic bearings use a different material than any other bearing on the market and are exclusive to Enduro bearings. XD-15 is a very special nitrogen infused steel material that will not rust or corrode. Even in contact with salt water or any caustic beverage you may spill, it will not be degraded or affected. Even the dirt or sand inside will not wear them out; it will simply polish the races smoother. The process of producing this steel involves remelting a very high quality stainless steel at the end of an electrode. This occurs in a highly controlled remelting chamber while introducing nitrogen gas, producing a homogeneous steel with ultimate fatigue resistance. A super strong, solid steel perfectly coupled with Grade 3 ceramic balls, XD-15 bearings get better over time. While other bearings are better the day you buy them and then break down, XD-15 bearings get better over time. Not only will you save watts, but you'll also save on maintenance. The XD-15 is the ultimate in b...