The KL6 LED conversion head provides your M3, M3T, orM4 with high-intensity LED technology. This is no typical low-output LED system – the KL6 uses selected ultra-bright 5-watt LEDs. When powered by three 123A Lithium batteries the KL6 produces a maximum of 65 lumens of light (more than a typical four D-cell alkaline flashlight) for 95 minutes, and provides over 4 hours of total useful light. Runtime is even longer when the KL6 is fitted to the M4 body. LEDs not only provide the ultimate in shock-resistance, they also provide extended runtime since they produce light more efficiently at low wattage; a battery too depleted to run an incandescent lamp can still produce usable light from an LED. The KL6 is CNC machined from aerospace-grade aluminum and coated in a military specification Type III hard-anodized finish, and features an anti-reflective coated Pyrex® window. The KL6’s digital current regulation circuitry matches the LED's current requirements with battery output, maintaining a more consistent level of light output for the useable life of the batteries, unlike unregulated lights that are subject to a steady decline in light intensity beginning shortly after activation. This circuitry also protects the LED module from current and heat-related damage. Many LED flashlight manufacturers inflate the light output and usable runtimes of their LEDs, but SureFire provides realistic output and runtime specifications based on scientifically obtained measurements. Athough any LEDs can produce negligible light output for over 100 hours, the amount of useful light produced is of a shorter duration.