Sightmark Solitude 8x42 XD Binoculars, XD (extra low dispersion) glass help correct optical color defects, caused when different light wavelengths do not converge at the same point after passing through optical glass. Engineered with Bak-4 roof prisms, the Sightmark Solitude 8x42 XD Binoculars yield an advanced, straight tube light system, achieving maximum light transmission and optimum brightness. The unit's prisms and lenses are fully broadband multi-coated, improvin