This combination focal reducer and field corrector lens accessory work with all Celestron C5, C8, C9.25", C11 and C14 telescopes. This clever accessory makes it possible to have a dual focal ratio instrument without sacrificing image quality. The Reducer/Corrector is f/6.3 for C5, C8, C9.25" and C11 telescopes and f/7.0 for the C14 telescope.