Genuine Kawasaki Z1 900 903 cylinder has been heat-treated powder coated. Comes with complete 1015 kit from Wiseco. This year does not take the center O-ring that the 74-75 take. Each piston is marked their respective cylinders. No 2 pistons are alike. 70mm. We use these kits on all of our restorations. *Optional enhancement, if you would like we can file the black from the edges of the fins to appear as the originals came.