Zhong Yi announced the new B4 to M4/3 2X extender:
UHD 4K + is a mount conversion extender adapter for mounting a 2 / 3-inch B4 mount lens developed by Zhong Yi Optics on a Micro Four Thirds standard camcorder. Equipped with a high-performance optical lens that doubles the focal length, the lens configuration is 8 elements in 5 groups, and by adopting a lens design optimized for the Micro Four Thirds image sensor, it supports up to 4K resolution (* used) If the B4 lens to be used is compatible with 4K).
The lens barrel is made of aluminum alloy, and the mount on the camera side is made of highly durable stainless steel used for cinema lenses. With a tripod mount that can be attached to and detached from an Arca-Swiss compatible standard tripod or pan head. (* Some are not supported.)