The Quad Tactical Headlamp from Princeton Tec is lightweight, durable, and ready to meet the needs of the military and outdoor sportsmen.Regulated Output: Princeton Tec lights feature regulated LEDs with a sophisticated regulating circuit that maintains constant brightness as long as the batteries have sufficient voltage. Through the Regulated Output period constant brightness, the light will maintain a certain level of lumens depending on the setting. Following this duration, the light will continue to work, though it will function at a lower lumen output. Lights without Regulated Output will begin dimming slowly from the onset, and will continue to dim until the battery is exhausted. They will not maintain a constant lumen output like that of Regulated Lighting.