I bought a couple of visual backs for my C9.25......then changed my mind. I'm selling the TeleVue unit in another add, this one I bought from Mercury Systems (one of AstroMarts Sponsers). It has two set screws and a brass compression ring (of course). It is just as nice as the TV unit and uses about 1/4" less back focus. It is brand new and I paid $32 plus shipping. Usable on any of the smaller SCT (C9.25 or smaller - I think). Yours for $30.