After several years of selling a variety of metal halide lamps we now only sell the best, the Sunmaster range from Venture Lighting. The overall market leader in grow lamps in the UK, the Sunmaster halides come in two different outputs; 4000 and 7200 kelvins. Blue light is measured in kelvins as opposed to lumens (which is the measure of light commonly used for sodium and dual spectrum lamps), the higher the kelvin value the more plant usable light the lamp gives out. Higher kelvin ratings result in healthier plants, shorter internodal length and increased yields later in life. The 7200K versions are slightly more expensive than the 4000K versions, but well worth the initial extra outlay with the benefits clearly showing later in the plants life. The 7200K versions are also the lamp of choice for adding extra blue spectrum to a lighting setup that contains mostly sodium lamps – adding approx one halide lamp to every two sodium lamps dramatically increases overall plant health, and is generally considered by most experienced growers as the optimum lighting mix. Highly recommended – these are by far the best metal halide lamps on the market and won’t break the bank.