The Coralife 27.75 inch, Colormax, 31 Watt T5 HO Fluorescent Lamps are 27.75 inches from end of pin to end of pin (for 30 inch fixtures/retrofits).
The Coralife 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 (24W, 31W, 39W or 54W) and NOs (9W, 14W, 21W or 28W). T5s are 5/8" or .625" in diameter.
