This is a set of 3 telescope eyepieces with SR4mm,F6mm, H12.5mm and H20mm focal length and 0.965" (24.5mm) fitting diameter, ideal for use on telescopes for target observation from short to long ranges. Features: Fully multi-coated glasses for excellent image contrast and light transmission The barrel end is threaded to accept sun/moon filters Plastic storage barrel to keep optics dust free when not in use 0.965" (24.5mm) fitting diameter Focal length: H6mm, H12.5mm and H20mm