Da Yi 6x12 roll film adapter

I have been looking into the Da Yi (which is Shen Hao?) 6x12 roll film back. I see a seller on the evil auction site that is offering them for $190 - hard to beat that price. Any idea if the seller is offering legitimate units? The unit looks functional but I don't know what the real thing looks like.

Also, anyone used one of these with a Chamonix 4x5? Shouldn't be a problem I would think.

Thanks.

I don't think that the Shen-Hao rollfilm backs are made by DaYi. There are several Chinese companies making very similar products.