Keep your holster, keep your tact lights, keep your favorite grips. LaserMax internal guide rods meet or exceed both Mil-Spec and Homeland Security durability test standards. If you can field-strip your gun, you can install your LaserMax sight. Pulsating gives effortless awareness of muzzle direction. Can be used outdoors or indoors. The Internal Guide Rod lasers come permanently aligned from the factory for center-of-mass accuracy at 20 yards. There is no need to re-zero after changing batteries. As close to the bore of the firearm as possible, positioning allows for the closest and most consistent relationship between your point of aim and point of impact over all shooting distances. Ambidextrous switch in custom take-down lever. Deliberate on/off activation. For: SIG SAUER P226 .40 cal. / .357 SiG Battery Model: LMS-392 (readily available silver oxide batteries commonly used in watches) Accuracy (20 Yards): ±2" POA Laser Operating Temperature: 15°-120° F Wavelength: 635nm (red-orange) Power Output: 5mW (brightest available - blinks for highest visibility) Spot size: at 7 yds 5/16”, spot size at 25 yds 3/4”.