Quantum Optical System incorporates Index Matched Lens coatings with lead-free, edge blackened lenses. DiamondCoat lens coatings on exterior lens surfaces. Up to 94 percent light transmission. Externally threaded, fast-focus eyepiece. Finger-adjustable 1/4-MOA click windage and elevation adjustments. Advanced power selector design incorporates a tactile power indicator and easy-to-read numbers. Second generation waterproofing with Argon/Krypton gas blend.