1 Material:optical glass,fused silica,CaF2 and optical crystal 2 Angle tolerance: 5" 3 Optical parallelism: 3' Roof prism is combined with a right angleprism and a totally internally reflecting roofattached to the hypotenuse. It can invert andreverse an image, also, deflect the image90... Therefore, it is often used in terrestrialtelescopes, viewing systems and rangefinders.Material:optical glass ...