Portland Oceaneering Undersize nylon insert?

OK nylon insert 3	OK nylon insert 4	OK nylon insert 1
undersize? Nylon insert 3	undersize? Nylon insert 1	undersize? Nylon insert 2

Backplate nuts on the Portland site

This, apart from the bold and colour, is from the Portland website and was correct as of 12/12/2004.
BACKPLATE NUTS - No Spanner required. Designed to complement Portland Oceaneering’s backplate range, these new and innovative nuts need no spanner. Beautifully engineered backplate nuts can be tightened by hand and unlike wing nuts they are very low-profile so won't dig in. Constructed from 316 marine grade stainless steel they have an in-built friction washer and are designed to fit an M8 thread.

And from an e-mail dated Sat, 11 Dec. 2004 10:13:44
The nylon insert on the 2nd nut does not appear to be threaded. This is in fact correct. The purpose of the insert is to provided a barrier between the stainless part of the nut and your backplate to prevent scratches.
Nut number one has slightly more nylon and a thread has been cut by screwing it onto an M8 bolt. This is not how the nut was designed but does not cause any problems.

Humm which is correct a barrier or an in-built friction washer? The nuts are indeed well engineered (at least the SS part) and very low-profile.

Unfortunately although the back plate is good and after placing an order the delivery was quick response to mail has been poor with about 8 e-mails unanswered after at least 4 working days and sometimes much longer.