Namura nx-40000-bk top end repair kit yz125 98-00 (NX-40000-BK) Top End kit includes: piston, rings, wrist pin, clips, topend bearing, and gasket kit MOS2 (Teflon/Molybdenum) Coated Skirts A rolled on application process provides a bond that is 10 times stronger than other spray on coatings. Benefits include increased heat transfer, reduced friction and helping to eliminate cold seizures. Machined Smooth Heads Reflects combustion heat and reduces carbon buildup, protecting the top of the piston. Some tests have shown this feature can increase horsepower and fuel economy by up to 6%