SureFire's DG series of switches enables the operator to maintain precise control over their weapon and light without compromising the grip on their weapon. These switches utilize a center mounted pressure pad, which allows the shooter to active their weaponlight with finger pressure while maintaining a full grip. This system is ambidextrous, and can be activated momentarily by pressing the switch forward/applying constant pressure. For constant-on, press the switch up or down. SureFire DG-19 Remote Grip Switch for Full Size H& K USP9/USP40/USP45 for X-Series WeaponLights DG-19