The AquaticLife 16.5 inch, Roseate 18 Watt T5 HO Fluorescent Lamps are 16.5 inches from end of pin to end of pin (for 18 inch fixtures/retrofits). AquaticLife Part# 410221. This is Bulk lamp. It's an AquaticLife branded lamp (the logo is on the bulb), but it does not include the retail packaging. It's comes in a plain brown box.

The pinkish Roseate lamp is 650nm and is ideal for freshwater planted tanks. Best used in combination with 6000K lamps.

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.