Pentax Weatherproof XW 5mm Extra Wide Eyepiece w/1.25 Barrel. These Optics by Pentax are built with high-performance high-refraction extra-low-dispersion lanthanum glass elements for crystal clear images and the proprietary multi-layer coatings on all lens surfaces deliver a light transmission efficiency of more than 90 percent over the visible light spectrum. The Pentax XW Multi-Coated Eyepiece is JIS Class 4 weatherproof constructed so you can use your eyepiece in light drizzle or even under night dew so you can be confident you're getting the best view in most weather conditions. Get the best view you can with this Pentax XW 31.7mm Sleeve Eyepiece Specifications for Pentax XW Extra Wide Fully Multi-Coated Eyepiece: Manufacturer: Pentax Condition: New Finish: Satin Color: Black Diameter: 1.25 in Field of View Angle: 70 degrees Eye Relief: 20 mm Lens Finish: Fully Multi-Coated Features of Pentax XW Extra Wide Eyepiece PX-4S-XW: Clear comfortable viewing assured by 70 degree apparent angle of view and 20mm eye relief High-grade optics for exceptional image quality Pentax original multi-layer coating for outstanding light transmission efficiency Advanced light-shielding technology for improved image contrast Weatherproof construction for all-weather viewing American-standard eyepiece sleeve and built-in adapter mounting screw Package Contents: Pentax XW Extra Wide Fully Multi-Coated Eyepiece Pentax 70512: Weatherproof XW 5mm Extra Wide Eyepiece w/1.25 Barrel