Top-quality piston kit featuring superior ring seal, bore compatibility, quiet running and longer lifespan 2,000 hours of durability testing behind every piston Auto-Fit Coating is a permanently bonded, moly-based coating process, designed to last for the life of the piston Auto-Fit Coating is a permanently bonded, moly-based coating process, designed to last for the life of the piston Accurate to a 30 micron thickness to deliver tight piston-to-sidewall clearances for ultra-quiet operation Gas nitride-coated rings offer the ultimate compatibility with nickel-silicon-carbide-plated bores Piston kits are intended for use with Revolution Performance big bore and Monster/big bore cylinders 114"/124" kit, 1999-2006 Twin Cam (flat top; 4.25" bore, 4" stroke; 11:1 comp)