plano-convex,double-convex,plano-concave,double-concave Material:BK7,Fused Silica,ZnSe,ZnS,Si,Ge,etc.,Specification ... °Paraxial Focal Length:±2% Specifications:Material: BK7 grade A optical glass, or other optical materialDimension Tolerance: +0.0, 0.1mmCenter Thickness: ±0 ...