Sunmaster lamps are dual spectrum bulbs that are suitable for use throughout the vegetative and bloom phases. During the growing cycle, many growers use a metal halide lamp which burns at “cooler” temperature. This doesn’t mean it isn’t as hot, but that it is more blue than an HPS lamp. When plants are in bloom, the grower switches to HPS which are “warmer”, being more red. While there are advantages to using separate lamps, sometimes only a dual spectrum will do!