Achromatic doublet lenses are designed to correct spherical aberration and chromatic aberration to get higher quality image. This performance can be achieved over a broadband of wavelength. Specification: Material: Cemented crown and flint glasses Focal length: +/-1% Diameter: +0.0/-0.03 Center thickness: +/-0.05 Centering Accuracy: 1' Figure (sphericity): 1~3 Surface Quality: 60/40 Coating: Optional