The HR15 Humidifier With Humidistat is a complete kit that helps the grower with maintaining relative humidity in the growing room. Optimum humidity is essential for healthy plant growth. The humidistat allows for a desired humidity to be set, so this important environmental factor can be completely controlled. In addition to controlling humidity levels, the Humidifier HR15 connects to any water reservoir and is great for rooms up to 30m2. Improve your plant growth and development. For use with soft, purified or RO water – do not use with hard water.