The Exo Terra Heat Lamp A21 150W is a high-wattage, broad-spectrum heat bulb (A21 shape) for large terrariums. It emits intense infrared heat and visible light to create a wide, warm basking spot that can raise the overall terrarium temperature. This 150W heat lamp is ideal for large reptiles that require very warm basking areas, and it should be used with a heat-resistant fixture. It provides essential warmth for thermoregulation, aiding digestion and activity in heat-loving species.