Hybrid aspherical lens elements for edge to edge sharpness in any lighting condition. Scratch resistant coating on exposed lens elements. Fully waterproof and fogproof, nitrogen filled, submersible to 1 meter. Helicoid 4 stop eyepiece ring for comfortable eye relief. Phase-coated roof-prisms for a sharper view. lightweight magnesium frame. Fully multi-coated lenses for increased light transmission. Inner-focus optical design. protected by a limited lifetime warranty.