Dual Arc (HPS+MH)
To learn more about HID lighting read our buyer's guide. HID Lighting Buyer's Guide. Dual Arc grow bulbs make it possible to use one lamp from seed to harvest, including your vegetative and blooming phases. These single light sources have the most varied spectrum because they include Metal Halide (MH) and High Pressure Sodium (HPS) bulbs, often a 600 watt HPS and a 400 watt MH to comprise a 1000 watt bulb.