There are some exceptional products out there in this day and age that challenge the view that the only way to make permanent repairs is by welding or soldering. A lot of it has been developed in the aviation industry with the flow-on effect that we get to use it to play around with it for our cars

I had a look at that 'Fastcool' listing Donkey. The OE part number listing at the top is correct for the XJ81 V12, some of the others with cross-referenced listings are wrong though. Best bet would be (as per the parallel thread about this issue!) to call with some detailed questions about the actual item.
Best,
Starbuck