1,Size: Standard 1.25 inch or 31.7mm universal eyepiece for astronomical telescopes. 1.25 inch 4mm eyepiece gives the widest viewing field along with extra sharpness. 2,Telescope Eyepiece: 4mm focal length eyepiece for wide field of view and superior performance. Foldable eyecup allows for comfortable viewing, even with glasses. 3,Fully Coated: Offers bright and sharp images with excellent color correction for planetary viewing and daytime observation. Fully coating group on each lens surface maximize light transmission, contrast and gets clear images 4,Features: All metal construction with a threaded bottom for 1.25in filters, compatible with standard 1.25 inch interface telescopes or filters. 5,Widely Used: Suitable for all astronomical telescopes with a 31.7mm interface. Perfect for broad field lunar observations, medium sized star clusters, and a wide range of cloudy nebulas and deep sky targets. Item Type: Telescope Eyepiece Material: Aluminum Alloy, Optical Glass Weight: Approx. 57g or 2oz Focal Length: 4mm or 0.2in 1 x Telescope Eyepiece 1 x Storage Box Note: Due to the light and screen setting difference, the item's color may be slightly different from the pictures. Please allow slight dimension difference due to different manual measurement.