It would appear that there are a batch of incorrect connectors going around at the moment, as this was the first one of many of these I have ordered that won't fit any graphics card available on the market today. The wiring is perfect, but the connector is completely the wrong shape to fit the power connector.
The photograph shows the "correct" 6-pin layout, with 4 rounded (R) pins and 2 square (S) pins, as so:
but what I actually received was the following:
which a simple Google search will indicate does not exist at all to fit any graphics card ever.
So I returned it, but I leave this review as a warning for anyone looking for this type of adapter: The correct ones appear to be completely impossible to find, email sellers first.