Celestron 93444 Ultima Duo Eyepiece, 1.25/2-Inch, 17mm (Black) High performance photo-visual eyepieces quickly switch between observing and imaging Fully multi-coated optics with 8 elements in 5 groups for the best correction of chromatic aberration and field curvature Extra wide 68-degree apparent field of view Full 20 mm of eye relief Integral 42 mm T-adapter threads and threaded barrel for filters