SPROCKET and Hub, Single, #50 chain, 19 teeth; 1.36"ID x .37" wide keyway x 5.00" wide overall. Hub has 2 setscrews and lock nuts. Application: NH Models 818 and SP818, Engine Drive at Gearbox, 020 ENGINE SHEAVES & IDLER GROUP - 818,SP818. New OEM New Holland 36562