* If you are looking for a 10,000K daylight metal halide, you'd be hard pressed to find a better value than XM lamps. So, why use XM?
1) Unlike other 10,000K bulbs, XMs are designed to operate on common U.S. ballast specs. No need to purchase more expensive pulse start or HQI ballasts to run them.
2) If you own a metal halide pendant or hood system, the majority of the time, these ballasts are the correct type for XM lamps. No guessing needed.
3) A high performance, high quality lamp designed for the demanding aquarist! The price of these are favorable over competing 10,000K lamps. Just compare and see for yourself.
4) 100% Satisfaction Guarantee: if you are not happy with the XM lamps, you can return them within 30 days for a 100% refund!! (less S/H) Please see our return policy for full details.

FAQ:
Q. What are the ANSI codes for Probe Start and Pulse Start ballasts?
A. Probe Start ANSI Codes for Metal Halide lamps: M102=150W, M57=175W, M58=250W, M59=400W, M47=1,000W.
Pulse Start ANSI Codes for Metal Halide lamps: M85=70W HQI, M81=150W HQI, M137=175W, M138=250W, M135=400W.
Q. What is the deal with "pulse start" or "probe start" ballasts?
A. "Probe start" ballasts are more common in the U.S., while "pulse start" ballasts are more common overseas. Most aquarium lighting hoods and pendants sold here in the US have PROBE start ballasts, as most MH lamps sold here are made for those ballasts. However, the short list of PULSE start style lamps commonly sold in the aquarium trade would be: 175W and 400W Ushio 10,000K, and both 250W and 400W Radium 20,000Ks. Those lamps will generally operate fine on pulse start ballasts, and we see little to no problems. We sell both pulse and probe start ballasts so you can get the correct one for your lighting needs.
Q. Why do 10,000K bulb all have different colors? Shouldn't they all be the same if they're marked "10,000K"??
A. Color Temperature ratings (i.e. "K") is more of a marketing term than a true scientific measurement for color. There are far too many variables when it comes to an accurate "K" rating. Bulbs of the same manufacture can color up differently over time, as the ballast ages (although this is generally not noticeable by the aquarist). This is why most "K" is used as a reference rather than an absolute. The higher the K, generally the more "blue" the bulb becomes. Sunlight is about 5,500K.
Q. All these color temperatures seem confusing. Which one should I go with?
A. Always ask yourself what's most important to you and your tank specimens. If you are an SPS keeper, and your goal is growth, then we suggest 250W or 400W Iwasaki 6,500K bulbs. If you have lower light corals and want a "deep water" look, then go with a 20,000K bulb. If you want "crisp white", then go with an XM 10,000K. Just remember that any new bulb that you have never tried will look different to you, as you've grown accustomed to the previous type. Visual color is a matter of personal preference.