An LED lamp is a light-emitting diode (LED) product that is assembled into a lamp (or light bulb)) for use in lighting fixtures. LED lamps offer comparatively long life compared to incandescent lamps and some fluorescent, although at a higher initial expense. Degradation of LED die and packaging materials reduces output over time. Research into organic LEDs (OLED) and polymer light-emitting diodes (PLED) is aimed at reducing the production cost of lighting products. Diode technology currently improves at an exponential rate. Some LED lamps are made to be a directly compatible drop-in replacement for incandescent or fluorescent lamps. An LED lamp packaging may show the lumen output, power consumption in watts, color temperature and sometimes an equivalent wattage of an incandescent lamp it will replace. Efficacy of LED devices continues to improve, with some chips able to emit more than 100 lumens per watt. LEDs do not emit light in all directions, and their directional characteristics affect the design of lamps. The efficacy is generally higher than incandescent lamps. The light output of LEDs is small compared to incandescent and compact fluorescent lamps and in most applications multiple LEDs are needed to form a lamp. LED chips need controlled direct current (DC) electrical power and an appropriate power supply is needed. LEDs are adversely affected by high temperature, so LED lamps typically include heat dissipation elements such as heat sinks and cooling fins.