Chrome plated finish. It greatly helps; when trying to maximize airflow through a filter; to have a large filtering area. But building a huge filter was a no go; it had to be small and very effective. This is where the Arlen Ness design artists started. Adding the inside surface of the air cleaner to the outside adds a huge amount of filtering area. With the integrated radiused air inlet this air cleaner showed some of the highest flow numbers that Ness ever tested. The final look give air cleaner a very small custom and attractive velocity stack look that will effectively pull in air from all sides and additionally provide you with more legroom. Filter elements are made from synthetic material. They resist water; a rain sock is usually not required. Filters are re-usable; just rinse clean and re-install. Oiling is not required. Note: Breather design is o-ringed at the heads; passes through the backing plate and is placed inside the mouth of the throttle/carburetor body. This eliminates external breather hoses so nothing will be taken away from the clean look. Note: See 590444 for the optional rain sock. Usually not required but can be used when desired in exceptional heavy downpours. Note: See 590397 for the replacement filter element with chrome trim ring or 590396 for the filter element with black trim ring.