I kept seeing kits with a Namura top end set and a cylinder.. I finally went to their site and couldn't find a complete kit with a cylinder, just the top end parts. I contacted them and they said they don't offer cylinders and that any kits I see are pieced together but not by them. Other than the Namura kit, I wasn't able to find anything else like that so I'm going to "assume" this is an oem cylinder. Powerseal told me OEM was cast iron sleeved and this is cast iron. I can run around town dealing with a local machine shop but just to be done with it, going to send it probably to Powerseal since I have used them before and they were a little cheaper than Millennium and that bike is still running fine after 7 years.