RTS HD Pro aluminum case kits offer large bore sizes for the highest splined axles. They use superior 206-T4 heat-treated aluminum, which has 12 percent more yield strength and 32 percent higher tensile strength than the commonly used 356-T6; it's also substantially lighter than an iron case. HD Pro kits are designed for drag racing or abusive street/strip applications with high horsepower and torque. They feature a billet pinion support with 360 degree channel to maximize oil flow to the pinion bearing, as well as two contact points with the bore of the case--which holds the pinion shaft more securely for improved bearing and gear life. Their oversized tail bearing handles more load and greater rpm; billet main caps with chromoly studs support the carrier bearings, while significantly reducing ring gear deflection.