Orion 7725 14.21-Inch ID Off Axis Solar Filter White-light solar filter fits Orion SkyQuest XT12 Dobsonian telescope and XX12 Truss Tube Dobsonian telescopes for great views of sunspots and the solar surface Safely covers entire telescope aperture, with a 4" off-axis glass filter which allows safe solar viewing Filter inside diameter is 14.21" and each Orion telescope solar filter fits tube diameters up to 0.25" smaller than specified size 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