Shortens Minimum Focusing Distance. Extension tubes are used to reduce the minimum focusing distance of the lens mounted. The Fujifilm MCEX-16 noticeably decreases the focusing distance. You can check this magnification chart for a rundown of possible focusing distances.

Electronic Contacts. The built-in electronic contacts enable both autofocus and autoexposure capability, as well as transferring lens information to the embedded image EXIF data.