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 glassesFocal length: +/-1%Diameter: +0.0/-0.03Center thickness: +/-0.05Centering Accuracy: 1"Figure (sphericity): 1~3Surface Quality: 60/40Coating: Optional