Looking for grow lights? Our a la carte lighting allows you to choose the reflector, ballast and high intensity discharge bulb that best fits your needs and budget. Keep in mind that the bulb you choose will depend on your ballast. For example, a 400 watt HPS bulb will only work with a 400 watt HPS ballast (or 400 watt convertible ballast). A Metal Halide bulb must be used with MH ballasts (or convertible ballasts) of the same wattage. Conversion bulbs provide added flexibility and can be used with either type of ballast.