Material：BK7 Optical glasses,CaF2,BaF2,
                                       MgF2,Ge,Si,Fused Silica
                             Diameter Tolerance :+0.0/-0.02mm
                             Thickness Tolerance : ± 0.01mm
                             Surface Accuracy : λ/4 @632.8nm
                             Surface Quality : 20-10
                             Centration : 1'
                             Clear Aperture : > 90%
                             Bevel : 0.2×45°
                            Coating: user-defined