The bulb emits infrared heat rays and is a typical heating lamp. The spot lamp has a special built-in reflector to direct the heat in any desired direction. The red glass transmits the infrared rays generated by the special filament of the bulb. The reddish light does not interfere with normal activity during the night or day, making it an excellent 24-hour heat source. The Exo Terra Glow Light is perfectly suited for the Exo Terra Incandescent Bulbs.