The XW 20 eyepiece is designed for use with a wide range of PENTAX spotting scopes and telescopes. Ideal for both ground and astronomical observations, this eyepiece features fully multi-coated lenses to increase light transmission and colour quality, high-refraction lanthanum glass elements for high-resolution images with minimal aberrations, and JIS Class 4 weatherproof construction for durability. Engineered using advanced computer simulation design technology, this high-performance eyepiece provides a 70 degree field of view and 20mm eye relief.This Eyepiece is Compatible with the PF-65 and PF-65 ED II series spotting scopes, PF-80 series spotting scopes, PF-100 series spotting scopes.- Improved 70 degree field of view for wider views- XW 3.5mm, 5mm, 7mm, 10mm, 14mm, 20mm, 30mm, and 40mm provide a wider field of view than previous PENTAX eyepieces- All Pentax XW series eyepieces may be used with astronomical telescopes with appropriate 1 ?? or 2? focusers- XW 3.5mm, 5mm, 7mm, 10mm, 14mm, 20mm eyepieces may be used with our PF series Spotting Scopes (except PF 63 Zoom)- Full multi-coated lenses increase light transmission and contrast- High refraction, extra-low dispersion lanthanum glass elements deliver bright, high resolution images with minimal distortions and aberrations- Advanced computer simulation design technology implemented to drastically reduce internal reflections, producing brighter, clearer images- Weatherproof construction for greater durability- Long eye relief for comfortable viewing with or without glassesSpecifications:- LENS STRUCTURE: 6 elements, 4 groups- FOCAL LENGTH: 20mm- APPARENT FIELD OF VIEW: 70 degrees- EYE RELIEF: 20mm- ATTACHMENT DIAMETER: 1.25 (31.7mm)- FILTER DIAMETER: 28.6mm- FIELD STOP DIAMETER: 24.0mm- EYEPIECE RING: Helicoid type- DIMENSIONS: 3.4 x 2.4 in- WEIGHT: 12.6 oz. (355g)- LENS STRUCTURE: 6 elements, 4 groups