| Specifications: | |
| Material: | N-BK7, Fused silica or other optical glass |
| Dimension Tolerance: | +0.0, -0.2mm |
| Surface quality: | 60-40 S/D |
| Surface flatness: | λ/4 @ 632.8nm |
| Angle Tolerance: | ±30 arc sec(Standard); ±5 arc sec(High Precision) |
| Clear Aperture: | >85% of dimension |
| Bevel: | <0.25mm×45° |
| Coating: | Surfaces S1 & S2 :Single layer MgF2 coating |
| Surfaces S3 & S4: Aluminized and painted black |