Namura NX-40001K 53.94mm Top End Kit Namura pistons are made to exact OEM specifications and are direct replacements for OEM pistons with no modifications or dimensional adjustments needed Top-end kits come with the piston(s) individually wrapped, a set of OEM quality rings packed in their own box, wrist pin(s), circlips and include head, base and other necessary gaskets, O-rings and valve guide seals, as required Namura pistons have MOS2 (Molybdenum/Teflon) skirt coatings, high-silicon aluminum and anodized domes A, B and C top-end piston kits are available to help extend the life of expensive Nikasil, SCEM, Boron Composite and Ceramic Cylinders Namura rings are made by Riken, the world's largest OEM manufacturer and are the same OEM rings used on more motorcycles and ATV's than any other brand