Easy to Use: This telescopic eyepiece features 8-24mm continuous zoom that can be viewed at different times depending on your needs. The eyepiece is equipped with internal threads for easy installation.Function: This telescope eyepiece is mainly used in astronomical telescopes which are suitable for observing the sky and landscape, as well as observing the moon, planets and mists .High Quality: The retractable eyepiece body is made of metal, CNC machined, delicate texture, comfortable feeling, durable. Note: This product is only suitable for home and astronomy hobbyists, not for professional astronomical research. 20mm eyepiece: This retractable eyepiece features a standard 1.25 inch astronomical interface and is extremely versatile. The 20mm eyepiece offers more comfortable observation. Advantages: The telescopic eyepiece features an all-metal lens body, multi-layer anti-reflective green film and excellent optical performance that ensures a clear image. Note: Data are all measurements manual, please allow 1-3cm error, due to the light and display difference, there will be some color difference, depending on the physical object received.