Function : 1. High-quality eyepiece with full multi-layered coating , with the possibility of zoom to any focal length from 7mm to 21mm, selecting the best magnification for your subject. 2. To watch the prince life, planets, nebulae, star clusters and other bodies celestial and astronomical observations, high dispersion, wide field of view, very comfortable. 3. good as design, suitable for 1.25 inch / 31.7 mm astronomical telescope. 4. The zoom eyepiece is not just an eyepiece, high magnification to low magnification, focal length to telescope, easy to adjust proportions, very practical. 5 . Professional production, metal body, surface coating, excellent optical parameters. Specification: Item Type: Eyepiece Matter : aluminum alloy optical glass Black colour how many : 1 piece distance focal length: continuous zoom 7-21 mm Lens Coating Film: Broadband Green Film Weight : approx. 168g Interface Size: Approx. 31.7 mm / 1.25 inch Package List : 1 x eyepiece