24 watt T5 HO TrueLumen Actinic Purple 420nm TrueLumen 39W Actinic High Output T5 Lamp. 34 inches from end of pin to end of pin (for 36 inch fixtures/retrofits) Actinic, 420nm Purple The TrueLumen T5 bulbs will work in any T5 fixture, as long as you are using bulbs of the same wattage and length as those currently in your fixture