Specification:

Material: BK7 Grade A Optical Glass
Dimension Tolerance: ± 0.2mm
Thickness Tolerance: ± 0.2mm
Flatness: l/4 @ 632.8 nm per 25mm
Surface Quality: 60/40 scratch and dig
Parallelism: 1 arc minute
T/R: 50/50± 5%, for natural light
        T=(Ts+Tp)/2, R=(Rs+Rp)/2
Coatings: (Incidence angle: 45 degree)
S1: Single wavelength partial reflectance
S2: Multilayer AR coatings