Via Egami Blog (Japanese)
This one, for what I have seen for the first time, can change the back focus distance so as to make the lens short-sighted (for macro purpose) if required. The above adaptor is for Leica M-mount lens to Sony NEX E-mount. Below are some more additional information about the possibilities of the adaptor when used with particular Leica M lenses:-
http://leicarumors.com/2011/06/16/leica-m-to-e-mount-helicoid-adapter.aspx/
And an example adapted combo:-
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