Metal Halide lamps have a strong blue spectrum, which promotes short stocky vegetative growth. The Agro Sun Classic bulb has 38%, the Agro Sun Gold has 49%, and the Sun Master Warm Deluxe has 50 percent more red light spectrum than a regular Metal Halide lamp. This will result in increased flowering and production from plants. These bulbs allow you to grow different plants at various stages of growth, while only using one lamp. (All lamps have a shipping weight of 5 pounds.)