Specifications:
Material: BK7 grade A optical glass
Dimension Tolerance: +0.0, -0.2mm
Clear Aperture: >85% of diameter
Deviation: 180deg 5 arc seconds
Flatness: lambda/4 at 632.8nm on big surface, lambda/10 at 632.8nm on other surface
Wavefront Distortion: lambda/2 at 632.8nm
Surface Quality: 60-40 scratch and dig
Bevel: 0.25mmx45deg                                                                         
Notes: Other sizes and coatings are available upon request. Lower price for lower
precision is aviable.