With this diagonal you can match the orientation of the star field with "correct" star maps and charts. It produces an that is oriented properly, which means that the is upright but reversed from left to right. This is a great diagonal for daytime terrestrial use and night time astronomy applications for telescopes or spotting scopes. Features - Color: Black. - Size: 8.50X3.50X4.50cm or 3.34X1.38X1.77 inch. - Material: Plastic, glass. - Note: Screw is random style. - Standard inch diameter fits for 0.965 inch eyepiece and telescope focuser. - Designed for refractor and catadioptric telescopes, and not for reflector telescope. - Wide 90 degree angle allows you to view the correct from the refractor telescope stand and just look down at a comfortable angle. - Easy to install and use. Just insert into 0.965 inch telescope at the silver end, the other end fixes 0.965 inch eyepiece by the screw. - The body is constructed of materials, sturdy and not easy to damage.Packing list1 x Zenith Mirror