This is a replacement Traxxas X-Maxx Constant Velocity Steel Driveshaft. This X-Maxx steel constant-velocity driveshaft is for use with the for 8S-spec heavy duty drivetrain. For the older 6S truck, you can used this driveshaft as an upgrade but it also requires the following parts: 7751X, 7754X, and 7768 or 7768R to complete installation.