This 50.8mm Mirror Diagonal from Vixen was designed to be used with Vixen refractors and catadioptric telescopes to accept 2" (50.8mm) eyepieces. This mirror diagonal is beautifully designed using matte black paint with anti-reflective threadings, giving you the best viewing experience. This aluminum mirror is also able to yield high light transmission. The safety stop at the bottom of the eyepiece holder prevents collisions with the mirror, preventing any aberrations that may occur. You'll notice the difference between viewing through a 2" eyepiece/diagonal combination versus 1.25" flip mirror system- a wonderful experience!