This is the Fotodiox battery conversion adapter ZJ-01. It's an adapter that came with a light I bought, or perhaps it was part of a set. When attached to lighting that uses V-mount batteries, I think it allows operation with large NP-F batteries. It has been stored unused, so I've only checked with a tester to ensure there are no disconnections. Looking at the official website, it's about $40, so I'll list it for half price including shipping. Shipping will be via Takkyubin Compact. Instant purchase is OK. I am also selling a set of 2 separately. Please ensure a smooth transaction.