I modified it

I put my Keystone electronic ballast in my fixture and it fits. And I tested it for an hour and thirty, and nothing had happened. And don't worry, the ballast is grounded for safety. I didn't like that small exposed circuit board, because if it fails, it starts to smoke. So putting in a enclosed ballast is best to prevent smoke.

I also put holes on top of the fixture where the ballast is. So it can breathe while in operation.

So now, I can put F20 T12 in this fixture since the ballast is capable of running a F20 T12 tube.