The M17 and M18 pistols have been selected by the US Military as the official sidearm, and the ROMEO-M17 is the only optic that is truly designed specifically for this pistol. All other optics have many disadvantages and make several compromises. The ROMEO-M17 does not. This is an American-built MIL-SPEC red dot truly worthy of the SIG SAUER name.Please Note - The ROMEO-M17 pistol red dot sight utilizes SIG SAUER'S proprietary SIG-LOC mounting interface and only fits SIG SAUER M17/M18 military issue, and commemorative pistols with a single optics plate mounting screw. This sight will not fit any other pistols.A fully enclosed, sealed, and purged optical system, for ultimate protection from the elementsMounts from underneath the pistol slide, re-using the MHS pistol rear sight block and sight block screw7075 Aluminum housingIntegrated gas deflector on the front of the housingMachined anti-reflection grooves on all rear surfaces for reduced glareExtremely low deck height, allowing a full sight picture and co-witness with standard-height sightsSIG-LOC(TM) (SIG Leverage Optimizing Connection) proprietary mounting interface, for the ultimate optic/pistol lockup.A high-efficiency point source LED emitter, with 2 MOA dot/32 MOA circle reticle. The reticles are independently selectable (circle only, dot only, or circle/dot combination).Independent brightness adjustment buttons that are recessed within a protective plate which can be activated even with gloves on. Buttons have bump features above UP and below DOWN, so they can be determined by feel.15 brightness settings, with 3 of the settings optimized for use with Gen 3+ NV devicesA side-mounted CR2032 battery compartment with a threaded battery cap, for easy battery changes without the need to remove the optic from the firearm. The cap is slotted and knurled, for use with or without tools.Minimum continuous runtime of 20,000 hours, at medium brightness setting2 drainage holes machined in the sides of the housing, just behind the rear sealed window, to allow pooled liquid to escape when the optic goes from a vertical position (such as in a holster) to a horizontal position (such as shooting)Windage and elevation adjustments have tactile clicks. Adjustment screws are slotted, for use with any small flat-blade tool. Adjustment resolution is 1.5 MOA per click.MOTAC (Motion Activated Illumination)MAGNETAC (Magnetic Activation)D.A.R.C. (Dark Adaptive Reticles & Coatings)Designed, developed, tested and fully assembled in the USA