Material: BK7, Fused Silica, Sapphire, etc. Dimension Tolerance (mm):±0.1 (General), +0.0/-0.01 (High Precision) Surface Quality: 60/40 (General), 20/10 (High Precision) Clear Aperture: >90% (General), >97% (High Precision) Parallelism: <1arc min. (General), <10arc sec.(High Precision Flatness (per 25mm@633nm):<λ/2 (General), <λ/10 (High Precision) Bevel (face width x 45.):<0.25mm (General), No Bevel (High Precision) Chip (mm):<0.2 (General), <0.05 (High Precision)