it is 5" long splined shaft. Problem is the gearbox end is round, and every coupler kit uses D style ends. I've called 6 "listed" keystoker dealers from their website. That paper might as well be used in the small room... Most of the so called dealers have no idea what a Keystoker is? The original one had aluminum ends with a setscrew, with the splined tube connecting them. Any ideas where to purchase?