These are our patented Reptile T5HO UVB + Double GU10 Basking Light Fixtures that provide UVB and basking in one streamlined fixture that is easy to mount underneath the habitat's top screen mesh. Reptile 22" T5HO UVB + Double GU10 Basking Light Fixture is recommended for use in our 36x18x24, 36x24x24 and 36x18x36. Reptile 22" T5HO UVB + Double GU10 Basking Light Fixture is also recommended for superior flexibility with our 36x18x18 and 36x24x18 terrariums; instead of the Reptile 22" T5HO UVB + Single GU10 Basking Light Fixture. These are the best fixtures that we've ever used for our reptiles' UVB requirements! This T5HO (high output) fixture gives superior performance because of its high output electronic ballast and its high-efficiency silver reflector. UVB is necessary for your reptile's synthesis of vitamin D3, which is essential for the effective metabolism of dietary calcium in its bones and blood. We prefer the UVB output from linear fluorescent tubes because this way it's possible to cover 2/3's of the habitat area; that way the reptile is benefiting from UVB exposure as it moves about the habitat. This fixture is a superior addition to the habitats of bearded dragons, Rankin dragons, horned toad lizards, uromastyx, most other desert reptiles, small turtles and tortoises. Animal should be no closer than 10” directly under the fixture and no closer than 6” diagonally from the sides or ends of the fixture.