Sorry forgot about that, there's only 2 engines I'm talking about. The engine I run and it works good is a fantom '03 rear exhaust, the one I just got from a friend is an OPS rear exhaust, no part number on the box and nothing on the case other than "OPS". This one looks decent and isn't the odd or goofy looking ones that I've seen from them in the past. I don't have a digital camera but if you'd like maybe I can describe the how the engine looks.