This is an aftermarket replacement NEW output shaft for your 18-spline or 25-spline Getrag gearbox - it goes out from the transmission to the transfer case to drive the rear wheels. It's not uncommon for the teeth/splines on the end of the shaft that mates up in the transfer case to strip or even break off entirely, yielding no power to the rear wheels, and essentially crippling the car into an undriveable state. :(
If that has happened to you, then this is your solution!
20x6x6 / 5lbs