I am almost used up my supply of T12 Reptisun 10 tubes and the new ones at the store are now T8 only. I know that T8 tubes can fit into T12 fixtures and actually work but it would depend on whether the T12 fixture is rated to handle the T8 tubes (some can take both). I asked around how to tell if my fixture can take what kinds of tubes, and everyone says "It should say on the ballast, open it up and read what it says on the ballast". My question is, what the heck is the ballast and where is it? Can someone show me a picture?