Powerful white-light-emitting diodes (LED)s are increasingly replacing incandescent bulbs in practical flashlights. LEDs existed for decades, mainly as low-power indicator lights. In 1999, Lumileds Corporation of San Jose, California, introduced the Luxeon LED, a high-power white-light emitter. This made possible LED flashlights with power and running time better than incandescent lights. The first Luxeon LED flashlight was the Arc LS, designed in 2001. White LEDs in 5 mm diameter packages produce only a few lumens each; many units may be grouped together to provide additional light. Power LEDs, drawing more than 100 milliamperes each, simplify the optical design problem of producing a powerful and tightly-controlled beam. LEDs can be significantly more efficient than incandescent lamps, with white LEDs producing on the order of 100 lumens per watt, compared to 8-10 lumens per watt of small incandescent bulbs. An LED flashlight will have a longer battery life than a comparable output incandescent flashlight. LEDs are also less fragile than glass lamps. LED lamps have different spectra of light compared to incandescent sources, and are made in several ranges of color temperature and color rendering index. Since the LED has a long life compared to the usual life of a flashlight, very often it is permanently installed.