MACHINED SMOOTH CROWNS: A machined, smooth piston crown should reflect combustion heat while reducing carbon buildup and protecting the top of the piston. Some tests have shown that a very smooth machined crowns can increase HP and fuel economy by up to 6%.HARD ANODIZED CROWNS - STRONGER SURFACE: 75% stronger than non-anodized. Heat resistant with minimal expansion/contraction.MOS2 SKIRTS Teflon/Molybdenum blended coating. Non-abrasive, proven to have very high durability.SILICON CONTENT - HYPEREUTECTIC CAST Increases hardness of the aluminum. More resistant to wear and scuffing, less heat expansion and tighter clearances.