Orion Premium Zoom Eyepiece High-quality zoom eyepieces lets you pick the optimum magnification power for your viewing object Delivers exceptionally crisp, sharp images through-out adjustable focal length of 24mm to 8mm Fully multi-coated seven-element lens assembly with apparent field from 40-degrees to 60-degrees Long eye relief so eyeglass wearers can view in comfort 1.25" barrel diameter