I thought it was the tubes, bought new ones, but it's two, two-tube fixtures in a recessed space. All they did was flicker. So I avoided using those lights so it wouldn't burn out the ballast in each fixture. It wasn't the tubes. I don't have a problem replacing a ballast or two, but I can't find that damn plastic material which goes underneath the bulbs to spread the light. Checked at Home Depot. It was so old, brittle, and yellow that a lot of it broke apart when I tried to remove it. A little help?