The Harrington bumpers are marketed as being 'to original style / spec / fit' so far as I can understand these things.
On receipt, I noticed that the main cross section of the rear bumper was NOT square / would not sit flat on a flat surface.
Harrington's view was that it might still fit, but they inspired no confidence in me if that was their standard. There are plenty of blogs out there from other buyers expressing various concerns. The 275 rear body on the Z3 is slightly wider where the side sections wrap around and this complicates the fit between the sides and the main rear section. I may find a little further improvement.
Harrington do not give tolerances for their products.
At £1500 I did not expect a sub-standard part.
It is all too easy to see the 'beating out' marks on the metal; they are clearly not pressed out, which Ferrari maybe. They are well polished. The metal is thinner than I would expect. They are painted black inside. The appearance overall is not unsatisfactory. They do look very good, design wise, for this car.
Currently there is very little alternative for a set of stainless bumpers [for a number of cars]. Perhaps in future, with quality scanning, things will improve. These days an old car can be scanned and whole panels made as 'exact' replications. Chroming plastic is a growing area of technological advance . . .
Knowing what I now know, it is probable that I would buy the same again.
You are welcome to come and see them.