you cut up your stock ones or same to get the gray part. and yeah you need a slim ballast. and I found the plug to fit into the stock harness so I did not cut anthing.
i sold them a while ago as I swapped to early tails so I could have 3 total bulbs and on the early lights i couldnt use the HIDs without surgery so sold them
but I was happy with them you just learned to wait a second for them to get going LOL
I back into my garage
and I need to see the middle line as I park right on it so they worked well wit my really dark tails I had.