Materials: Bk7 A glass, Quartz
Focal length: +/- 1%
Length tolerance: +/- 0.1mm
Width tolerance: +/- 0.1mm
Center thickness tolerance: +/- 0.1mm
Centration: 5 arc minutes
Surface precision: 0.5 fringes/cm
Surface quality: 60 to 40 stretch/dig
Clear aperture: 90%
Coating: no or AR