The BAK4 prism with an anti-reflective coating and integrated high-quality optical prism instead of a mirror enhances accuracy; making it ideal for precise astronomical observations and ensuring clear and sharp images The inclusion of 2 Inch-1.25 inch adapters allows for seamless connectivity with both 1.25 Inch and 2 Inch accessories; catering to a wider range of requirements This wide 45 degree angle makes you view correct image from telescope stand; makes it easier to observe All aluminum black anodized with smooth surface and have long service life The product has a matte black internal thread design to prevent stray light reflection; additionally; the attachment design includes brass clamping rings and large chrome-plated thumb screws for a safe and secure connection without causing damage Precision Prism - Image erecting BAK4 prism with anti-reflection coating. - High accuracy and high light reflection prism. - Brass compression ring. Superior Craftsmanship - Internally matte blackened and threaded for no internal stray light reflection. - Threaded for 2" filters. Ready to Go - 1.25" adapter with brass compression ring included. - Large, chromed thumbscrews. Beautiful Finish - Entirely aluminum, black anodized. - Smooth finish. Features: - Prism: High quality BAK4 with anti-reflection coating - Materials: Entirely machined aluminum - Angle: 45 degree - Prism clear aperture: 31mm - 2"-1.25" adapter with brass compression rings. If there is any problem of focusing due to the light path for a few telescopes, please feel free to contact us for help.