Hydrofarm Agrobrite FLT5264 T5 Fluorescent Tubes, 6400K, 24 Watt, 2 Foot, Pack of 4 T5 replacement tubes offer HO light output at a great price. 24W puts out 2000 initial lumens per tube. Available in 4 packs. Full daylight 6400k spectrum, rated for 10,000 hours of life.