The Gavita Pro 600W / 400 Volt HPS Lamp is a single-spectrum lamp with the most plant-useable light output of just about any 600 Watt lamp on the market. The lamp produces light only in the orange/red part of the spectrum for heavy flowering. It has been specifically designed to make the most of your HPS Pro (400 Volt / 600 Watt) system where it will produce more plant-useable light photons, of a better spectrum, than any other 600 Watt lamp available. This lamp is for use with a 400v ballast or complete fixture. Do not use it with a standard 230v ballast.