And then insert the 2 bolt bracket ballast that come with a hanger layout into a steel box must be selected to match the wattage. This image is used with 20 Watt ballast bulbs 20 Watt or 18 watts.
Then add ballast mounting nuts 2 is not bundled. To the steel box Must be selected to match with this wattage ballast bulb 20 watts to 20 watts or 18 watts.
Add ballast holder nut 2 that he and me with a steel box, choose to Watts. This picture matching ballast 20 watts used with tubes 20 watts. Or 18 watts.