1Standard 25 Inch Diameter: 25 inches 90 degree zenith diagonal mirror fits for 25 inch focuser and eyepiece, works with refractor and catadioptric telescopes, not recommended for reflector telescopes. 2Stable and Reliable: 25 inches 90 degree zenith diagonal mirror can be used with refrator telescope and makes the image upright. Though left and right reversed, not affect astronomical observation. 3With Dust Covers: Fully coated lens come with dust cove, keeping your lens clean for superior image fidelity. 4Wide 90 Degree Angle: You can view correct image from refractor telescope stand and just look down with a comfortable angle . 5Durable Material: 25 inches 90 degree zenith diagonal mirror is made of aluminum alloy, ABS and plastic material, which is durable.1 x Zenith Mirror2 x Dust Cover