Special Milled Sprocket nut for the 9t sprocket application. This nut pairs with the X30 and KA 100 drive sprockets, 9T to give clearance for the chain.
Each sprocket nut is designed to fit and accommodate the chain as shown.
The Nut is a 17mm hex head nut, and comes with a milled spacer washer that also fits between the sprocket and the main nut.