The Zoo Med PowerSun(R) UV is a self-ballasted mercury vapor lamp. These are all-in-one lamps that give off light, heat and UV rays (both UVA and UVB) at the same time. This makes them great for creating a healthy basking area for any reptile, including your box turtle.
The UV light penetrates farther than standard UV bulbs, so if you have a tall habitat to keep your boxie from escaping, enough UV can still get to him.
In smaller enclosures this bulb might be overkill and could heat the whole thing too much (you may have to experiment with where to put it to avoid this).
You do need to use the PowerSun bulbs in a ceramic socket (no plastic or other materials), but you don’t need an external ballast (a ballast controls the electrical current to the light). So they’re almost as easy to use as a regular bulb, but they give your pet all the light and heat he needs.
It is important to note that these bulbs do contain mercury. But so do the compact fluorescents we’re all being forced to switch to, so that shouldn’t make much difference at this point. It’s just something to keep in mind.