Detailed Product Description SWA 20mm Telescope eyepieces: Prod. Code :BGWA20Focal Length(mm) :20Lens Structure(# ... :16Barrel(in) 11/4Field stop(mm):25.0FEATURES of SWA 20mm Telescope eyepieces:Super wide angle 70 degrees, high index glasses ... extremely high resolution. Fold-down rubber eyecups, filter threads, blackened lens edges, anti-reflection threads for maximum contrast, upper barrels are ...