Durability is the major factor when deciding between aluminum or steel rockers. With every cycle an aluminum rocker arm endures it moves one step closer to failure. The "magic of steel" is that as long as it cycles at less than its maximum failure point, it can cycle for virtually a lifetime without any issues. Steel rocker arms also maintain the ability to remain rigid and not flex with increased rpm. Chrome-moly steel is used to produce these new steel rockers, which is 300 percent stronger than extruded 7075-T6 aluminum; the strongest of aluminum materials. Plus, these arms feature a fully rebuildable design and a lifetime warranty against breakage.