The Nikon TC-20E III 2x Teleconverter is an exceptional teleconverter optimized for use with FX and DX digital SLR cameras. It doubles the focal length of compatible Nikkor lenses. The TC-20E III is constructed of 7 elements in 5 groups and with Nikon's Integrated Coating (IC) you will see improved color and reduced flair. It has one aspherical lens element which virtually eliminates lens aberrations.