Namura (NX-40025-BK) 66.36mm-B(0.01mm) Top End Repair Kit Fits: Yamaha YZ250 1999-2001 These include everything you need to get you operational again; they come with pistons, a top end gasket kit and bearings where needed Features MOS2 (Teflon/Molybdenum) Coated Skirts, a rolled-on application process provides a bond that is 10 times stronger than other spray on coatings for increased heat transfer, reduced friction, and helps eliminate cold seizures The Machined Smooth Heads reflects combustion heat and reduces carbon buildup, protecting the top of the piston increasing horsepower and fuel economy by up to 6 percent Anodized Domes increase heat resistance and durability; pistons with anodized domes are 75 percent stronger than non-anodized pistons