Specifications Material: BK7, Grade A fine annealed Diameter Tolerance: +0 /- 0.10mm Thickness Tolerance: +/- 0.10mm Surface flatness: Lambda/4 Surface quality: 60 - 40 scratch and dig Coating: Aluminized with MgF2 protection layer Reflectivity: R > 50% @ 120 - 200nm, R > 70% @ 200 - 850nm Angle of incidence 45°