3.68" ID Set of Orion Binocular Solar Filters Full-aperture optical glass filters deliver superb views of the Sun, and sunspots, without risk to your eyes or your binoculars' optics Orion white light glass solar filters for bincoulars provide better contrast and a more natural color than Mylar filters Elements are machine-polished and triple-coated with advanced nickel-chromium stainless steel alloy Each Orion binocular 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 binocular Note: All Orion binocular solar filters are designed for use with an adequate friction fit. Thumbscrews should ONLY be used to keep filter securely in place once a friction fit has been achieved