The Speed Booster Ultra 0.71x Adapter for Leica R-Mount Lens to Micro Four Thirds-Mount Camera from Metabones allows a Leica R-mount lens to be mounted onto a Micro Four Thirds-mount camera. While doing so, the adapter's optics help to maximize the connected lens's apparent angle of view while providing a 1-stop increase for the camera over the lens's aperture range.

If a lens intended for 35mm film or similarly-sized full-frame camera sensors is connected to a camera with a Micro Four Thirds-sized sensor, it would project an image larger than the Micro Four Thirds sensor was built to accept. Able to capture only the center portion of the projected image, the effective angle of view of the lens would be narrowed, creating an in-camera "crop factor." The Speed Booster Ultra 0.71x Adapter for Leica R-Mount Lens to Micro Four Thirds-Mount Camera condenses the light from a lens designed for 35mm film or "full frame" camera sensors and projects it onto a Micro Four Thirds sensor. This allows a Micro Four Thirds sensor to utilize more of the light gathered by a connected lens, which effectively reduces the crop factor while making available to the sensor an additional 1 stop of light for each of the lens's f/stop settings.

This adapter is constructed from aluminum alloy for durability while minimizing weight and its mounting rings are made with brass to further prevent wear-and-tear. Inside are five lens elements in four groups that are designed to provide optical clarity as well as color fidelity, and a detachable tripod foot is included that features 1/4"-20 threads as well as compatibility with Arca-Swiss tripod heads.

The Speed Booster Ultra 0.71x Adapter for Leica R-Mount Lens to Micro Four Thirds-Mount Camera does not support electronic communication between an attached camera and lens. To help determine the amount of light that enters a Micro Four Thirds-mount camera when using this adapter and a Contax/Yashica-mount lens, users should use the aperture ring found on the lens.