1、Zoom Eyepiece for Telescope: 7‑21mm zoom eyepiece equivalent to multiple eyepieces, obtain higher magnification with short focal length. It could bring you a better observation experience in a comfortable situation with high contrast imaging. 2、Versatile Use: For viewing moon, planets, nebulae, star clusters and other heavenly body landscape and astronomy observation, high dispersion, wide field of view, very comfortable. 3、Comfortable Viewing: Eye relief range of 15mm and 40 degree‑57 degree wide angle field of view ensure a relaxing and comfortable viewing experience for everyone, especially those with glasses. 4、Sturdy and Lightweight Construction: Matte black aluminum alloy housing is rugged yet lightweight, resistant to moisture and rust, ensuring stable performance even outdoors. 5、Fully Multi Coated Optics: Fully multi coated eyepiece reduces glare, eliminates reflections, increases light transmission, and enhances image contrast. 5 element 3 group premium optical design for superior optical performance. Item Type: Zoom Eyepiece Material: Aluminum Alloy, Optical Glass Weight: Approx. 179g / 6.3oz Focal Length: 7-21mm Continuous Zoom Lens Coating: Broadband Green Film Interface Size: 1.25 Inches Color: Black Field of View: 40 Degree-57 Degree 1 x Zoom Eyepiece 1 x Front Lens Cap (Pre Installed) 1 x Rear Lens Cap (Pre Installed)