Optical Crystal Bk7 Spherical Glass Lens Specifications Material---fused silica , BK7 FL tolerance--±0.5% Dimension tolerance--±0.05mm Thickness tolerance---±0.05mm Edge Thk.Variable(ETV)---≤0.02mm Clear Aperture--≥95% S/D---80/50~20/10 Flatness---lambda/4@632.8nm Centrality---≤3′ Dimension---φ3.00~50.80mm(convex,concave,prism) Manufacturer of Optical Crystal Bk7 Spherical Glass Lens