Dimension Tolerance: +0.0, -0.2 mm
Clear Aperture: >80%
Angle Tolerance: <30 arc seconds
Flatness: L/2 @632.8 nm
Surface Quality: 60-40 scratch and dig
Roof prism is combined with a right angle prism and a totally internally reflecting roof and they are attached by them largest square surfaces. It can invert and reverse an image, also, deflect the image 90° . Therefore, it is often used in terrestrial telescopes, viewing systems and rangefinders.