The HDS uses state-of-the-art digital electronics design. Twenty brightness levels ensure proper brightness control in either low light or very bright sunlight. An on-board microprocessor provides automatic battery check indicator, up/down brightness scrolling and programmable auto shutdown features. All electronics are fully encapsulated in shock absorbing resin compound.OperationOptics: Transmission holography - 100% parallax freeMagnification: 1x unlimited eye reliefTemperature:-20 to 150F (operating); -40 to 160F (storage)Sealing: Waterproof (submersible) & fogproofColor/Finish: Non-reflective black with hard coat finishAdjustment (per click): 0.5-Inch at 100 yardsAdjustment Range: +/- 40 MOA travelMount: 1-Inch Weaver dovetail/Picatinny rail (Mil spec 1913)Return to Zero: Repeatable to 1 MOA after remountingHeads-Up Display Window Optical Surfaces: Anti-glare and scratch resistant coatingsWindow Dimensions: 1.20-Inch x 0.85-Inch (30 x 23 mm)Window Material: Shatterproof laminate (3/16-Inch thick)Field of view (100 yards): 30 yards (28m) at a 4-Inch eye reliefStandard Reticle: 65MOA ring with quadrant ticks with a 1MOA Aiming dotReticle Contrast Ratio: 28,000:1 brightest to lowestNight Vision Contrast Ratio: 10,000,000:1 with NV switch engagedElectrical Power Source: 2 x -InchN-Inch alkaline batteries (available anywhere)Battery Life: 70 hours at nominal setting 12 (AA batteries: 350 hrs)Brightness Settings: 20 settings with scrolling featureAuto Battery Check Indicator: Flashing reticle upon startup if batteries are at 20% of battery life.Auto Shutdown: At 8 hours - programmable to 4 hours-Model 550 AA-Order code 552.A65/1-Night Vision Compatible -Waterproof & Submersible To 33 ft depth -Battery AA Alkaline-Battery Life 900 hours continuous-Length of sight54 inches (131 mm)-Reticle Options 65 MOA ring w/ 1 MOA dot-Weight: 8.8 ounces (250 grams)