SV47 Binoculars for Adults, 8X32/8X42/10X42 Bak4 Prism HD FMC Lens Waterproof fo
Pure optical fully multi-coated lens and BAK4 Prism. Type bak4 glass is a fine,dense optical glass that removes glass effctively internal lighting reduces light losses,but the price is more expensive generally used in high-end optical products.