The filter is threaded and can directly connect to the threaded eyepiece for easily installation The filter is equipped with a box, which is not easily to scratch and can loss The filter is designed with a metal frame for durability and Standard 1.25inch thread size: 1.25inch / 3.17cm thread size, suitable for most telescopes; The color filter has grooves that are easily to screw into the eyepiece lens Easily install and use, a great for astronomicals lovers, Manufacturer: HZBB