The Snypex knight d-ed 10x42 ed (extra low- dispersion) glass prevents chromatic aberration because it gives the designer of a multi-element objective lens more options to concentrate and direct the wavelengths of light more effectively, thus they can control and minimize aberrations, in particular, chromatic aberration. Snypex knight optics dielectric binoculars use an apochromatic (apo) lens design that includes high density ed glass elements and the use of the very best quality coatings like dielectric, a fully multi-coated optics, phase correction coatings back-4 on the roof prisms, with a wide field of view, generous eye relief combined with a very comfortable and functional open bridge body design that are both fog and waterproof, nitrogen-filled, lightweight as well as strong because of magnesium/alloy body on the knight d-ed 42mm .