I would contact them, Alex.
Keep in mind that the ballast in a fixture produces a specific wattage, and HO tubes/bulbs are higher wattage than regular T-5 tubes. Thus your T-5 fixture would not burn those t-5HO tubes as brightly. And the reverse is true as well. A T-5HO fixture would burn a regular T-5 tube brighter than normal, shortening its life. There is also a heat issue. You can change a ballast though. At least this is what I understand. I could be completely wrong.
