Don't forget to open the box before you buy the Bay ballast and make sure it has an electrical outlet. Some of them are just wiresto be wired directly into your building or house wiring.
Keep in mine also, when dealing with an internal ballast it WILL get VERY hot, almost as hot as the bult, so make sure its not sitting on or attatched to anything that will burn.
I HAVE seen those burn THROUGH an end table, and burn off cheap aftermarket light hangers.
Make sure your chain or whatever your hanging with can hold up to 100+lbs this should ensure the metal is thick(strong) enough to take the heat.
Just my take
becareful and have fun