Orion 07798 4.57-Inch ID Full Aperture Solar Filter (Black) A must-have for safely observing the sun and sunspots without damaging your eyes 4.57 inch Inside diameter optical glass filter fits snugly over your telescope's front aperture to block 99.999% of incoming sunlight for safe observation and astrophotography Glass filter elements are machine-polished and triple-coated with nickel-chromium stainless steel and fits telescope tube diameters up to 0.25 inch smaller than specified size of 4.57 inch Each Orion telescope solar filter includes three equidistant 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