70° Apparent Angle of View, 20mm Eye Relief, plus Weatherproof Body for Multi-Application Viewing Clear, Comfortable Viewing Assured by 70° Apparent Angle of View and 20mm Eye Relief All smc PENTAX XW-series eyepieces feature an extra-wide 70-degree apparent angle of view and an extra-long 20mm eye relief to deliver an exciting, wide-perspective image. High-Grade Optics for Exceptional Image Quality The high-performance XW-series optics incorporates high-refraction, extra-low-dispersion lanthanum glass elements to produce a well-balanced image with minimal aberrations. It is particularly designed to reduce the disturbing blackout effect by effectively compensating the spherical aberration of the pupil. PENTAX-Original Multi-Layer Coating for Outstanding Light Transmission Efficiency All lens surfaces that come in contact with air are treated with the original multi-layer coating, while all laminated surfaces are treated with the innovative partial coating, to offer the light transmission efficiency of more than 90 percent (an astonishing 96 percent at 550nm) over the visible light spectrum. Advanced Light-Shielding Technology for Improved Image Contrast Thanks to PENTAX’s advanced computer simulation technology, the XW series features a light-shielding diaphragm at the most effective position to drastically reduce internal reflections for a brighter, higher-contrast image. A Choice of Six Magnifications to Meet Specific Applications With four different magnifications (3. 5mm, 5mm, 7mm, 10mm, 14mm and 20mm) to choose from, the XW series accommodates a wide range of both casual and specialized applications. Weatherproof Construction for All-Weather Viewing The XW series features JIS Class 4 weatherproof construction*, making it possible to use it in drizzle or under night dew. * The XW-series eyepieces are not designed for underwater use and should not be submerged under water. Standard Eyepiece Sleeve and Built-In Adapter-Mounting Screw The XW series features the American-standard 1. 25” tube (31. 7mm) for smooth, easy installation on the ANY telescope and/or PENTAX spotting scopes. When the rotatable eyecup is removed, it also offers an optional adapter-mounting screw/thread (43mm in diameter with a 0. 75mm pitch).