LaserMax Guide Rod Laser meets or exceeds both Mil-Spec and Homeland Security durability test standards (drop tests, blowing sand, temperature and humidity extremes, salt water, fog, deep water immersion, 20,000+ rounds live fire). It has an on/off switch on the takedown lever. No gunsmithing required to install. These pulsating red lasers install as the internal guide rod as close to the bore as possible for a close point of aim/point of impact relationship. Factory aligned for center-of-mass accuracy at 20 yards, they never need realignment, even after changing batteries. The ambidextrous on/off switch is located in the custom take-down lever for deliberate activation.