Where do you start? What are the options? Should you consider a retrofit kit or use a 360 degree post top screw in bulb? Here are some of the things you should consider before you purchase...
from
https://www.myledlightingguide.com/blog-how-to-retrofit-a-400-watt-hid
from
https://www.myledlightingguide.com/blog-how-to-retrofit-a-400-watt-hid
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