Coated air spaced glass doublet objective lens, 80mm clear diameter by 900mm focal length. Plastic mount with O.D. of 95mm and front lip to butt against a tube up to about 100mm O.D. Or you can insert a tube with an OD of 91mm. There is about 25mm of depth inside and a screw hole to fasten your tube tight. This is a great quality telescope objective and will make an excellent scope. Or get 2 for a binocular scope. New
