Material:  BK7 grade A optical glass 
  Design Wavelength:  632.8 nm, 
  Design Index: n=1.5147
  Surface Figure:  x: ¦Ë/2; y: 2¦Ë
  Dimension Tolerance: +/-0.2mm
  Paraxial Focal Length: +/-2%
  Centration: 3 arc minutes
  Clear Aperture: >80% 
  Surface Quality:  60-40 scratch and dig
  Bevel:  0.25 mm x 45¡ã