A good duty light should be easily carried on a duty belt, provide adequate illumination up to 50 yards away, and be long enough that it protrudes from both sides of a fist so the light can act as a last-ditch impact weapon. The light should also be able to be used in conjunction with a sidearm in the Harries or Rogers technique. Xenon bulbs put out a tight beam and mega amounts of lumens; but they eat batteries and the lamp assemblies are expensive when you need a new bulb. LEDs, on the other hand, are rapidly approaching the light output of xenon at 50 yards or so. These models became available in 2009.