From the ManufacturerThis 6.3 mm Sirius Plossl eyepiece is ideal for all types of telescopes: reflector, refractor, and catadioptric. Superb 6.3 mm focal length 1.25" eyepiece for high-power planetary and lunar observation in any telescope. Offers a 52-degree apparent field of view for clear, sharp views of impressively high contrast. Fully coated optics with magnesium fluoride on every air-to-glass surface to reduce reflection and increase light transmission. Eyepiece barrel threaded for use with 1.25" filters