The AquaticLife 16.5 inch, 6000K 18 Watt T5 HO Fluorescent Lamps are 16.5 inches from end of pin to end of pin (for 18 inch fixtures/retrofits).
The 6000K lamp provides a natural white light. It's appropriate for freshwater planted tanks and refugiums.
The AquaticLife T5 bulbs will work in any T5 fixture, as long as you are using bulbs of the same wattage as those currently in your fixture. T5 bulbs come in two categories, HO bulbs (18W, 24W, 31W, 39W or 54W) and NOs (9W, 14W, 21W or 28W). T5s are 5/8" or .625" in diameter.
