Versatile: Building a custom set of headlights, and worried about moisture problems? These bolt-on breather vents are the perfect solution to let moisture exhale from your housings, without letting moisture in. Simple To Use: Drill a 12mm hole in your housings, insert the front-side of the breather vent in, tighten on the lock nut - and you're ready to roll! Better: Than the traditional moisture membranes, because they bolt-on rather than just stick on. Therefore, these headlight moisture vents won't ever fall off - and leave you with a big hole in the back of your housing. Pros: These are the new standard in the most professional way to keep your headlights dry. For the price, the piece of mind is priceless!