9.45" ID Orion Full Aperture Solar Filter A must-have for safely observing the Sun without damaging your eyes - optical glass filter fits snugly over your telescope's aperture to block 99.9% of incoming sunlight Fits Orion SkyQuest XT8 Classic Dobsonian, XT8 PLUS Dobsonian, XT8i IntelliScope Dobsonian, XT8g GoTo Dobsonian, Atlas 8 EQ and SkyView Pro 8 EQ, 8" f/3.9 Newtonian Astrograph, and more Each Orion telescope solar filter is mounted in a foam-lined aluminum cell featuring three equidistant securing thumbscrews, 4x 1/16" thick adhesive foam tabs, and 4x 1/8" thick adhesive foam tabs for customized friction fit to your telescope Filter inside diameter is 9.45" - fits 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