The Pentax 8.5 mm XF Series Eyepiece is a standard single focal eyepiece with a focal length of 8.5 mm, providing 46x magnification for detailed, high-contrast observations. It features an apparent field of view of 60 degrees for wide, immersive viewing and is specifically optimized for Pentax PF-65ED/EDA 65 mm spotting scopes, but fits any spotting scope with a standard 31.7 mm American thread. Constructed with high-refractive, low-dispersion lanthanum glass elements, it delivers high-resolution images with minimal aberrations. The eyepiece includes Pentax's proprietary smc full-surface multi-coating to enhance light transmission, as well as an advanced computer simulation design that reduces internal reflections for brighter, clearer images. It offers a long eye relief of 18 mm and a retractable eyepiece ring with four click-stop positions for comfortable use during extended observations. Built with JIS Class 4 weather-resistant construction, it ensures durability and waterproofing, making it reliable for outdoor activities such as birdwatching and nature observation. This eyepiece is a successor model of the XF series, focusing on precision and reliability without exaggerated claims.