Material: High grade BK7, UV grade fused silica glass, 
  or SF11
Incident beam deviated by 90o or 180o
Widely used in telescopes, periscopes, optical delay
  systems.

Right-Angle Prism Specifications

Dimension Tolerance:+0.0, - 0.2mm
Flatness: λ/6 at 632.8 nm
Surface Quality: 20-10 scratch and dig
Clear Aperture: >80%
Bevel:  <0.5 mm x 45o
Angular deviation tolerance: < 1'
Coatings: HR coating with R>99.5% on the reflection
    surface;  AR coating with R<0.2% on the input and
    output surfaces are available upon request .