Key Features 
Speed Booster ULTRA
Sharper corners, less distortion, reduced vignetting 
New optical design:  advanced 5-element/4-group optical design incorporating ultra-high index tanatalum-based optical glass to achieve extraordinary optical performance with improved corner sharpness, distortion and reduced vignetting.
Like the revolutionary original Metabones Speed Booster announced in January 2013, the Speed Booster ULTRA has a magnification of 0.71x, and so it effectively reduces the crop factor of mirrorless cameras with DX-sized sensors, such as Sony E-mount and Fuji X-mount cameras, from 1.5x to 1.07x.  However, the new ULTRA design makes very effective use of exotic materials at the furthest limit of glassmaking technology, and as a result is well corrected for use with virtually all fullframe SLR lenses regardless of exit pupil distance. Thus, the Speed Booster ULTRA performs extremely well with professional-grade f/2.8 zoom lenses such as the 24-70mm f/2.8 and 70-200mm f/2.8 zooms by Canon and Nikon to produce 17-50mm f/2.0 and 50-142mm f/2.0 high-speed zooms, respectively.  Similarly, high-speed fixed focal length lenses such as a 50mm f/1.2 will be transformed into a 35.5mm f/0.9 lens with excellent contrast and resolution from the center all the way to the edges of the image. (More information can be found in the press release here)
Key Features
Increase maximum aperture by 1 stop.
Increase MTF.
Makes lens 0.71x wider.
 Advanced 5-element/4-group optical design incorporating ultra-high index tanatalum-based optical glass by Caldwell Photographic in the USA (patent pending).
The tripod foot is detachable and compatible with Arca Swiss, Markins, Photo Clam ball heads.
Disclaimer: we are NOT licensed, approved or endorsed by Sony or Canon.
Optics designed by Caldwell Photographic in the USA (patent pending)

Description 

Why Metabones®?
Since its inception, Metabones has been designing and manufacturing lens adapters recognized among professionals and enthusiasts as leaders in design and workmanship.
Contrary to the popular trend of other factories using an aluminum ring painted black on the camera-body-side, we instead take no short-cut but use precision-machined brass with chromium plating on both the camera-body and the lens sides of our adapters, in order to ensure smooth mounting, great appearance, and durability. The lens side of the adapter features a strong leaf-spring structure, strengthening the adapter-lens connection and ensuring tightness of the lens in order to reduce wear and prevent focus errors and optical alignment issues from appearing.
Metabones uses matte-black treatment to keep internal reflection to a minimum in order to maintain the maximum optical quality possible with the lens.
All Metabones Adapters follow this tradition of uncompromising precision, robust build quality and outstanding finish. Our new Smart AdapterTM series of products add industry-leading electronic interfacing technology from Canada, with true electronic control of the lens' aperture directly from the camera body.
Features
Both camera-side and lens-side of the adapter are made of brass, precision-machined and plated with chromium.
Satin surface finish - just like your OEM lens and camera mounts.
Precise fit and solid connection - lens has no play, gap or wiggling when mounted on adapter and no adjustments are required to fit your lens.
Designed to reach infinity focus while maintaining the correct registration distance required to maintain optical quality of CRC lenses or lenses with floating elements.
Our Smart AdapterTM  series adapters have the following additional features
True electronic integration of aperture diaphragm - let camera automatically choose aperture in P or S exposure modes, or dial in yourself on the camera body in A or M modes.
EXIF data such as lens identification, focal length and aperture.