For use in both vertical and horizontal fixtures.
This is a MH bulb that works with an HPS ballast. If you bought an 600W HPS lighting system to use during the flowering stage, and now you want to use the same lighting system to grow plants in the vegetative stage instead, then this is the bulb you need. Simply unscrew the existing HPS bulb and replace it with this one.
NOTE: This bulb is slightly larger than a standard 600W HPS bulb.