High port flow gives great performance now, and more later when additional upgrades are done. Heads are fully assembled with springs and valves, and are available in silver or black powder-coat finish to match OEM components. Compression ratios vary depending on cylinder heads chosen, pistons used and engine displacement. Heads are machined for compression releases (sold separately); S&S rocker boxes required when using S&S compression releases. Do not include rocker arm components, intake manifold, gaskets or headbolts (requires eight long OEM length head bolts). Accept OEM intake manifolds. Sold in pairs. Made in the USa.