Since 1993, Sightron Scopes have built a reputation for excellent optical quality and reliably repeatable adjustments. The Fast Focus Eyebell is featured with all SIII Series Riflescopes. It allows for quick and easy adjustments when in the field and has a diopter adjustment range from -2.0 to +1.0 settings. Features a one-piece 30mm main-tube made from high quality aircraft aluminum. All Sightron SIII LR Series Riflescopes feature XACT-7 seven layer multi0coating with precision ground glass. These lenses provide superior light transmission and resolution for the ultimate in performance. These scopes also feature Sightron's unique Exac Track windage and elevation adjustment system. Round knurled dials are complete with positive clicks and are resettable. Scopes are Nitrogen filled and are fogproof and waterproof.