I've used them before and think their quite good. They're a combination UVB/UVA mercury vapor bulb--gives off UVB, UVA and heat--one bulb does the whole job. They can be quite fragile and should be hung vertically in a ceramic fixture (the instructions that come with the bulb will tell you that).
You can buy them as either a spot light or a flood light. Some people prefer the spots, I prefer the floods because the heat and light are diffused more (and therefore less chance of the turtle getting too hot and more lighting in the tank). Either gives off a lot of heat, and the optimal distance from the basking spot for the 100-watt flood is 12 inches if I remember correctly (they also come in 160-watts). They're not recommended for smaller tanks because of the heat factor. You can read about the flood light here:
www.reptiledirect.com/browseproducts/Ac ... Flood.html Also do a search and you can read about the spot light.
You should compare a few sites for prices--I usually buy my bulbs at
www.4littlepets.com or its affiliated site
www.reptiledirect.com"You become responsible, forever, for what you have tamed." -Antoine de Saint Exupery-
