Material: Grade A BK7 optical glass
Consisted of three mutually perpendicular faces and a
  hypotenuse face.
Beam entering the hypotenuse face is reflected and
  emerges from the same face with 180o  degree change in
  direction.
Widely used in distance measurement, optical signal
  processing, laser interferometer, and optical delay
  system.

Corner Cube Specifications

Dimension Tolerance: +0.0, - 0.2mm
Flatness: λ/4 on the perpendicular faces
                 λ/10 on the hypotenuse face
Surface Quality: 60-40 scratch and dig
Clear Aperture: >80%
Bevel:  0.2 mm to 0.5 mm x 45o
Angular Deviation Tolerance: +/-3"
Coatings: Metal coating on the three mutually
   perpendicular faces and AR coating on the hypotenuse
   face is available upon request .