Add an additional 10mm or 19mm of wheelbase extension to Revo, E-Revo and Summit in just minutes! Traxxas makes it easy by building the adjustment into the rear arms. Installation is a snap and the wheelbase can be quickly tuned trackside for any conditions. Select either 10mm or 19mm of extension by simply repositioning the pivot ball locations. Requires #5153R drive cups when using 5451R driveshafts.