Emits UVB a full 20"/51cm from the surface of the lamp to prevent or reverse metabolic bone disease. (Compared to 12"/30cm on the ReptiSun 5.0). Optimal for use with larger terrariums where greater than 12" of UVB penetration is needed. The ReptiSun 10.0 is also recommended for use above screen covers which can filter out up to 50% of the UVB wavelengths.