9.45" ID Orion Deluxe Safety Film Solar Filter Explore the Sun safely through a telescope with this high-quality solar filter featuring Baader AstroSolar film in a sturdy aluminum cell Fits Orion Atlas 8, Sirius 8, SkyQuest XT8, XT8 PLUS, XT8i, XT8g, SkyView Pro 8, 203mm f/4.9 OTA, 8" Ritchey-Chretien, 8" f/3.9 Astrograph, and more Each filter is mounted in a foam-lined, clear-anodized aluminum cell featuring three equidistant securing thumbscrews for secure telescope attachment This filter has an inside diameter of 9.45" - it is designed to fit optical tubes with an outer diameter of 9.2" to 9.45" with included shim materials and securing thumbscrews Note: All Orion solar filters are designed for use with an adequate friction fit attachment. Thumbscrews should only be used to keep filter securely in place once a friction fit has been achieved