Standard 0.965 inch diameter fits for 0.965 inch eyepiece and telescope . 0.965 inch 90 Degree Diagonal Adapter Erecting Mirror for Telescope. Designed for refractor and catadioptric telescopes, and not for reflector telescope. Features - Color: Black. - Size: 8.50X3.50X4.50cm/3.34X1.38X1.77 inch. - Material: Plastic, . - Note: Screw is random style. - Coated lens comes with cover; keep your lenses clean for images fidelity. - 90 degree diagonal mirror using a refractor telescope and makes the upright; though left and right reversed; not affect astronomical observation. - More comfortable viewing orientation as you observe from above, thread for any 0.965 inch . - A diagonal that is angled at 90 helps avoid neck strain when the eyepiece. - It is manufactured with professional technology to ensure the of the product and can work for a long time. Package list: 1 x Mirror