It features a built-in microcomputer for seamless communication among camera body, lens and extender, features careful lens placement and coatings to minimize ghosting, flare and chromatic aberration, and even has a new Fluorine coating that keeps soiling, smears, fingerprints to a minimum.
Extender EF 2X III meets necessary standards in terms of rugged, dustproof and water-resistant construction, and should be in every professional's camera bag.