FOUR PACK This is Bulk lamp. It's an AquaticLife branded lamp (the logo is on the bulb), but it does not include the retail packaging. The AquaticLife 45.75 inch, 60/620nm Purple 54 Watt T5 HO Fluorescent Lamps are 45.75 inches from end of pin to end of pin (for 48 inch fixtures/retrofits). AquaticLife Part# 410225. The 60/620nm Purple bulb spectrum is ideal for acroporas, anemones, clams, hard corals, leathers, mushrooms, polyps, soft corals and xenias. 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 (24W, 31W, 39W or 54W) and NOs (9W, 14W, 21W or 28W). T5s are 5/8' or .625' in diameter.