plano concave lens Material: flint glasses, UV-fused silica, Infrared fused silica, CaF2, Ge, ZnSe, Si, etc. Focal length: ¡À5mm --¡À1000mm¡À1% (test by TIROPTICS OPTOMATIC2000 made in Germany) Diameter: 4mm--200mm ¡À0.1mm Tc torlerance:¡À0.1mm Centration: 3-5' Surface accuracy: ¦Ë/2 Surface quality: 40/20 Clear aperture: 90% Coating: custom design