1.25" Telescope Eyepieces, Orion Sirius Plossl 1.25" eyepieces are ideal for all types of telescopes: reflector, refractor, and catadioptrics such as Maksutov-Cassegrains Sirius Plossls offer a 52-deg apparent field of view for clear, sharp images Fully coated with magnesium fluoride on every air-to-glass surface for excellent light transmission and high contrast views Comfortable built-in rubber eyeguards enhance viewing by helping block ambient light and positioning the eye Threaded for use with Orion 1.25" eyepiece filters