It is done with tint paint you get at the hobby shop. First you have to take the lights out and sand the out side so that it is dull, with a really fine grit. Then spray one thin layer at a time until it is as dark as you want it then top coat it. It is hard to do because if there are any runs or thin to thick parts it will show when the lights are on and look really bad. The only other downfall to it is there is no going back once you start sanding so be confident in what your trying to do. Blackouts are look good on the cars I've seen.