Vortex Optics Diamondback Classic Binoculars Fully Multi-Coated - Lenses Increase light transmission with multiple anti-reflective coatings on al Phase Correction - Used on roof prism models onlycoating enhances resolution and contrast. Roof Prisms - Valued for greater durability and a more compact size. Waterproof - Optics are sealed with O-rings to prevent moisture, dust, and debris from getting insid Fogproof - Argon gas purging guarantees superior fogproof and waterproof performance.