VHS-4305 has a Dead-hold BDC reticle MAG-View combines fiber optic magnification indicator with raised rear-facing references XD Lens elements extra-low dispersion glass increases resolution color fidelity for sharp images Proprietary XR fully multi-coated lens coatings increase light transmission for maximum brightness One piece 30 mm aircraft-grade aluminum tube delivers strength rigidity for improved accuracy optimum visual performace durability waterproofness O-ring seals prevent moisture dust and debris - results in waterproof performance Filled with argon gas to inhibit internal fogging :