Orion 07710 5.81-Inch ID Full Aperture Glass Telescope Solar Filter (Silver) A must-have to safely observe the sun without damaging your eyes - optical glass filter fits snugly over your telescope's aperture to block 99.9 percent of incoming sunlight Fits Orion StarBlast 4.5 and SkyQuest XT4.5 reflectors, AstroView 120 and 120ST refractors, StarMax and Apex 127mm Maksutov-Cassegrain telescopes, and other models Filter inside diameter is 5.81 inch - fits telescope optical tubes with an outer diameter of 5.56 inch to 5.81 inch with included shim materials and securing thumbscrews Each Orion telescope solar filter is mounted in a foam-lined aluminum cell featuring three equidistant securing thumbscrews, 4x 1/16 inch thick adhesive foam tabs, and 4x 1/8 inch thick adhesive foam tabs for customized friction fit to your telescope 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