The optical hardware 4x standard eyepiece set 125 has one of each of the 4mm6mm12mm20mm standard eyepieces with their 125 317mm barrel size to fit any telescope with a standard 125 inch fitting standard filter thread for fitting moon filters and light pollution filters etc and coated optics for better transmission and clarity these eyepieces are a great addition to any beginner telescoperr 125 317mm barrel size standard filter threadr coated for better transmission and