Here I have a 1/2" drive socket to fit the gearbox sprocket nut on the four speed triumphs , ie T120 , T110 unit and pre unit. its 1-11/16" ( 43mm ) across the flats and fits the nut correctly unlike some box spanners sold on this site ! It may fit other models as well please check the size of your nut first , the nut is not included . Overseas p/p is a estimate, please ask first .