"The URI Actinic White lamp is the first of its kind to offer a 50/50 combination of triband (daylight) and actinic (blue) phosphors. This mixture provides a great balance between the life supporting spectrum required by live rock, corals, anemones, and related marine life, and the daylight spectrum required for vibrant color rendition. The 180 degree internal reflector allows for 40% more light output. The Actinic White Lamp has a kelvin temperature of 12,000.
Excellent for all marine and reef applications."
If you want a balanced morning/evening look instead of full actinic blue. These would also be useful for fowlr and softie setups where no metal halides are used.