Fluorescent and compact fluorescent lamps are low-pressure discharge lamps with high light output and low power consumption. Conventional fluorescent lamps are usually rod-shaped or round. Compact fluorescent lamps, in contrast, have tubes that are bent, folded or coiled and therefore much smaller which makes them suitable for round or small lights. Due to their durability and high luminance, compact fluorescent lamps are also called energy saving light lamps. Lamps with socket E27 increasingly substitute incandescent lamps.