250 watt HQI ballast.

[Delphinus]

Originally Posted by ron101

So I will need to order two correct?

If you have two bulbs you want to fire, yes. One ballast per bulb, can't get around that one unfortunately. What they mean by "dual" (or "tri" or "quad") is the number of "taps." "Dual tap" means a lead for if you want to run it off a 110V circuit, and another in case you want to run it off a 220V circuit (they share the "common" either way). "Tri tap" would mean 110V, 220V, or 360 (?? not sure, something in the 300's anyhow) and "quad" means 110, 220, 360, or 480.

It depends on the application and what kind of power supply ya got in your location but basically for our needs we're just interested in the 110V tap. I suppose one could run a dryer or stove circuit and use the 220V tap but I don't know if there would be any real benefit to it.