Canon Extender EF2xIII Lens

2x increase of the lens's focal length
Dustproof and waterproof specifications (JIS 2 equivalent)
Lens placement and coatings are optimized to minimize the ghosting
Built-in microcomputer in the extenders enables communication between lens, extender and camera
Anti-smear coating (Silky Barrier Coating) used to enhance smear-free state of the lens surface