A power LED may be categorised as a single LED that emits a bright light and has a power output of 1 watt or greater. These are devices that are ready to be incorporated into a fitting or device, such as a torch, projector or appliance, and they usually have a cover or lens. Although supplied as a complete LED, some devices will require a separate driver that precisely controls the LED current, and for continuous use, a suitable heat sink. Power LEDs are available in a range of colours, such as red, green, amber and blue. When selecting a white LED, it's important to choose the right colour temperature, which may vary between 3000K and 6000K. A lower colour temperature provides a light that is warmer, while a higher colour temperature produces a very white or blue-white light. While most LEDs are designed for DC operation, it's also possible to purchase AC power LEDs. These typically incorporate a driver circuit and can be connected directly to 230 volts AC. As an alternative to power LEDs, LED fittings are supplied as completely ready-to-use fittings. Suppliers of power LEDs include Samsung, Seoul Semiconductors, Osram, Barthelme and Lumileds.