I purchased 6 Costco 4 foot LED's, nice and bright! They use the ballast. I tried running one without the ballast and it seems intolerant of that, but it did light up for a while. I found that they would not function properly on some of my electronic ballasts.
I also purchased 6 ballast bypass 4 foot LED's on Amazon, made by Hyperikon. It was a simple matter to follow the instructions and rewire the unit. Basically one removes the ballast by cutting the wires RIGHT at the ballast, then hook the existing wires right to the power wires, as directed. Simple, easy and very effective. They work wonderfully! I wish I had gone this route the first time.