... ' 3.Parallism< 1' 4. S/D: 20/10 CaF2, MgF2, ZnSe, ZnS, Ge, Si etc. 5.Flatness:1/5-1/10F ... , UVFS, IRFS and optical crystal material such as: CaF2,MgF2, ZnSe, Mono Ge, Mono Si, SapphireDia. Tolerance: +/-0.001 inchThickness tolerance ... : +/-0.001 inchS/D: 20/10 CaF2, MgF2, ZnSe, ZnS, Ge, Si etc. 10/5 BK7, FS, SF&SK ...