maximum OK, but not more

Even with these intermediate rings, only the connections of metal and the rest is made of plastic.
More suitable for small and lightweight lenses, as an addition to something weightier macro lenses, I would not use them.
The lens mount is held and fixed in the Mount of springs, unfortunately, the results that they have some play. If you are using one of the rings is not as extreme, if you really want to use all the time in combination, which can already be very clear.

For me, no article that would justify the price, was returned.