actually when it comes to crested geckos you want to use either the 2.0 or the 5.0, anything higher will produce to much UV for them. In some instances UVB bulbs can burn the eyes, but it has to be in points of where the UV is to strong, or the reptile is far to close. So in this instance the 8.0 and 10.0 would be bad choices for the crested gecko. But on the other point is great for bearded dragons.