Orion 7730 4.30-Inch ID Full Aperture Solar Filter A must-have telescope filter for safely observing the sun and sunspots without damaging your eyes or your optics Optical glass filter fits snugly over your telescope's aperture to block 99.9% of incoming sunlight Glass elements are machine-polished and triple-coated with nickel-chromium stainless steel Each Orion telescope solar filter includes three equidistant thumbscrews, 4x 1/16" thick adhesive foam tabs, and 4x 1/8" 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