Featuring a durable, shockproof, CNC-machined aircraft aluminum housing, the Sig Sauer® ROMEO3XL 1x35mm 6MOA Open-Reflex Sight is the ideal companion for sporting rifles, carbines, SMGs, optics-ready pistols, and tactical shotguns. Precision-molded aspheric lens technology virtually eliminates aberration, reduces weight, and focuses images through the lenses for superior optical performance, and a high transmittance red notch reflector delivers unmatched brightness, eliminates distortion, and maximizes light transmission for optimal clarity. MOTAC™ (Motion Activated Illumination System) technology automatically activates the 6 MOA illuminated red dot reticle when it senses motion, and powers down the unit when the weapon is idle for reliable battery preservation. 12 user-selectable brightness settings (10 daylight; 2 night vision) ensure reliable visibility in all lighting conditions, while the included low-profile 1913 Picatinny mount readily attaches to most firearm platforms for maximum versatility. The side-loading battery compartment makes it easy to replace the CR2032 battery (included) without removing the sight or affecting zero. Plus, the Truhold™ lockless zeroing system utilizes twin adjustment springs designed to withstand punishing recoil and deliver a quick return to zero, shot after shot. IPX7 waterproof and fogproof.