Seal It Up: Retrofit left the back side of your housings a bit open to the elements? These rubber housing caps may be your perfect solution to close that back up for good. Sizing: These rubber housing caps are available in a variety of diameters and shapes to fit the most common headlight flanges. To Measure: Measure the outer diameter of your headlight's rear flange and select from the size menu above. If you're over by +3mm, we recommend going for the next size up and using a large zip tie to secure them. Durable: These headlight accessories are made of durable black rubber, they won't harden or crack over time through from hot and cold temperature changes. Ribbed inner ridge works to keep them fit snugly to the backside of the housing. What else? Well...that's about it. They're rubber, they're housing caps, they keep crud out of your custom headlights. If you have a gap, you probably should order our rubber housing caps. That's all!