Maintain indoors gardens all year round. Hydrofarm's T5 replacement tubes offer high output light at a great price. 6400K Replacement Bulbs is rated for 20,000 hours of life per tube. Produces a full daylight 6400k spectrum. Compatible for all Hydrofarm T5 fixtures. 54W puts out 5000 initial lumens per tube. 24W puts out 2000 initial lumens per tube.