This is an accurate reproduction of the original 1915 / early 1916 style manifold. An original manifold was used to make the casting pattern and all machining was done by us on CNC equipment. The diameter of the bushing area is machined and sized to high accuracy. It is sized to fit the aftermarket brass packing washers currently available. The manifold is supplied un-plated so you can match the finish to the other brite work on your bike. Make sure to let your plater know to be careful of the bushing area during polishing. We would suggest protecting it with tape during polishing so the finely machined sealing surface isn't marred.