I don't know anything about it; I can only say that the 6K works perfectly and is easy to use; an alternative is the 4K, which is similar and with which you can expand the range of lenses enormously with the Speedbooster. A battery pack is recommended in any case.

At the moment, all manufacturers are struggling with production. Pandemic sends its regards. BMD could already produce, but the suppliers of the individual components cannot keep up with production.