Along with the 430 model, IceCap fluorescent lamp ballasts have been the industry leader for nearly twenty years. Rugged, reliable, and efficient are just some of the many accolades for this category classic ballast. The 660 can drive all VHO, PC and T5HO lamps in any combination up to 4 lamps, with a total not exceeding 440 Watts. It is fully dimmable when driving VHO lamps, operates silently, and is fully repairable with a 3-year warranty. It is a high frequency solution for aquarium, industrial, UV, germicidal, and horticultural applications.
This is from their website. They use to be the only dimmable ballast on the market. When they 1st came out the 660 was the only dimmable one of the two now the 440 and the 660 are dimmable. I just wan't sure if the T5's were dimmable.