This is a Rear Pro-Spline HD Axle pack for PRO-2 SC, Slash 2wd with ProTrac kit, Stampede 2wd and Electric Rustler. Pro-Line is proud to introduce the pre-assembled Pro-Spline HD Axles for the rear of the PRO-2 SC, Slash 2wd with ProTrac Kit, Stampede 2wd and Electric Rustler! The Pro-Spline HD Technology debuted on the Pro-Line PRO-MT Kit and is designed to handle some serious power. Made from Hardened Black Oxide coated Steel, the Pro-Spline Drive Shafts have a true 6-sided spline that slides smoothly throughout the suspension travel without having to worry about stripping out like the stock plastic drive shafts. The pins are held in place by zinc coated snap rings and M3 set screws on both ends (PRO Tip: Rotate snap ring so slit is away from the pin and put a drop of Tire Glue on the slit in the snap ring to prevent it from rotating. It is still removable with a flat-head screw driver). Are you looking for the Ultimate drive shaft Upgrade for the rear of your Traxxas Truck? Look no further than the Rear Pro-Spline HD Axles brought to you by Pro-Line!