A fully enclosed, sealed, and purged optical system, for ultimate protection from the elements; Mounts from underneath the pistol slide, re-using the MHS pistol rear sight block and sight block screw; 7075 Aluminum housing; Integrated gas deflector on the front of the housing; Machined anti-reflection grooves on all rear surfaces for reduced glare; SIG-LOC (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 devices; A 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 setting; MOTAC (Motion Activated Illumination); MAGNETAC (Magnetic Activation); D.A.R.C. (Dark Adaptive Reticles & Coatings)