The Spectrum 4.75" Full Aperture Glass Solar Filter- 111mm to 117mm is a premium quality solid glass filter meant for safe and comfortable solar astronomy, both imaging and visual. These economically designed filters provide natural, high clarity solar views for your perusal and use when used with an appropriately sized telescopes, and are made with high durability glass combined with high reflectivity coatings. The Spectrum 4.75" Full Aperture Glass Solar Filter is sized with an O.D. Measurement of 111mm to 117mm, leaving it the perfect size for use with a wide array of telescopes with matching OD's.