The EF 400mm f/4 DO IS USM is the worlds first super telephoto lens incorporating " Multi-Layer Diffractive Optical (DO) Element", for camera lenses, which corrects chromatic aberrations. By incorporating this optical element in the optical design, the EF 400mm f/4 IS USM is much smaller & lighter than a comparable lens having conventional optical elements. Comes complete with Canon ET-120 lens hood.