TheBlackmagic DesignURSA Mini Pro B4 Mountis a replacement mount for use on the URSA Mini Pro. This mount enables using your ENG-style B4 mounted HD lens on your URSA Mini Pro. The mount incorporates corrective optics that enable the use of a lens designed to work on a camera with three sensors and a prism, on the URSA Mini Pro, which is a single-sensor camera, without the image suffering from optical degradation.