Current SlimPaq high output T5 lamps are designed to deliver the maximum amount of lumens from the shortest possible length. These bulbs are extremely bright and can produce nearly twice the lumen output of a standard T8 fluorescent lamp of a similar length. We carry the 10,000K daylight bulb and both the 460 nm and 420 nm actinic bulb. Generally, 24 Watt bulbs are for 24" fixtures, 39 Watt bulbs are for 36" fixtures, and 54 Watt bulbs are for 48" fixtures. Be sure to check your original bulb before ordering. Feel free to call us with any questions at 248-840-2135 or toll free at 877-692-8552.