64 mm diameter U bolts
Fiat have such fat roof bars that I needed to buy new U bolts to attach our cycle carriers. U-bolts-R-us advertised the very thing I needed so I ordered 12. They didn't have enough in stock but made the others very promptly. When they arrived, 5 of them are good and the other 7 are not fit for purpose. I think the poor ones must be the newly manufactured ones. The problem with them seems to be that the thread is full of the galvanising so they will not take M6 handwheels as required. I have ordered an M6 thread cleaning die on ebay and hope that will solve the problem.
Stainless steel U bolts
I purchased stainless steel square top U bolts with fixing plate. They were of excellent quality and arrived really speedily. Exactly as specified - just make sure you read the dimensions correctly because the letters on the drawing don't seem to match the text giving the dimensions beneath the drawing.