1.25 inch 90 degree angle to that the images are upright, but left and right reversed A more comfortable viewing position and clear images The diagonal reflector are suitable for viewing celestial-bodies and good for land observation use Simply insert the erecting prism into the 1.25 "focuser and enjoy upright and right-angled images with your eyepieces Comfortable observation with 90-degree: Look pleasantly from into your eyepiece, filter thread for any 1.25" filter and accepts standard 1.25" eyepieces, Manufacturer: SkyPOOU