Celestron Granite Series Roof Prism Binoculars are the pinnacle of optical and mechanical design. Granite offers all the features youd expect from a top-of-the-line binocular, including ED (Extra Low Dispersion) glass. The ED objective lenses and fully multi-coated optics provide excellent sharpness and color correction, while virtually eliminating chromatic aberration. Granite also features BaK-4 prisms with phase and dielectric coatings to increase light transmission and overall image quality.