Hortilux High Pressure Sodium Bulbs allow you to give your plants the spectrum that they need for flowering. These Hortilux bulbs give excellent color with enhancement in the blue and violet spectrum; unlike ordinary high pressure sodium bulbs that do not emit light in the blue and violet spectrum. If you are going to use only one bulb for both vegetative growth and flowering, you should use an enhanced spectrum bulb. They also help to keep the plants from stretching in all phases of plant growth. These bulbs are available for 1000, 600, 430, 400 and 250 watt ballasts. They are universal burning bulbs which means that they can be used in any fixture, vertical or horizontal. These bulbs are environmentally friendly.