Upgrades your existing cheap prism or mirror diagonal (ie the ones you commonly get bundled with telescopes) for vastly improved resolution at the eyepiece. Superb finish - the nosepiece is chromed brass with an anti-slip recess and fully threaded for standard 1.25" filters. Internally flat-blackened to eliminate reflections for improved contrast. The eyepiece holder is black-anodised aluminium with a chrome cross screw. Screw-assembled mirror body in dense resin (ie not flimsy plastic), gives the whole unit a great quality feel.