Here is a description of the 10k XM bulb:
* 10,000K Color Temperature, without a 10,000K price!
* Excellent with or without Actinic supplementation (most prefer with Actinic).
* Operate on a probe start ballast, ANSI M58.
* Standard Mogul base.
* Will work on Hellolights 250W Electronic ballast and other 250W e-ballasts by other manufacturers.* Note: this bulb will not work on the Coralife Sun-System pendants. We do not carry any bulbs that will work with that item. Coralife has discontinued Sun-System pendants.