The size of the Exo Terra Repti Glo Compact Fluorescent bulb and its ability to be mounted vertically, or horizontally, make it a versatile UVB source for your turtle and tortoise. This bulb is self-ballasted with standard threading and a spiral shape. Combine this excellent UVB source with a Repti Glo 2.0 for a higher, visual light output to create optimal conditions. Check out the all of our lighting products at TurtleShack.com for a visual light and heat source for your turtle. Let us know if you have any questions!