Chrome-moly itself isn't any lighter than mild steel. The weight savings comes from the fact that it has a thinner wall thickness. Like a crankshaft, chrome-moly is an alloy, and is therefore stronger than mild steel. Consequently, the NHRA mandates 1.625x0.118-inch tubing for mild steel cages and 1.625x0.83-inch tubing for chrome-moly cages. Despite its thinner walls, 4130 chrome-moly tubing features a 106,000-psi tensile strength compared to mild steel's 63,000-psi rating.