Hello, first time here in this forum, I have tried to educate myself from the recent posts but didn’t found the answer… just bought Denso’s spark plugs for my XKR y2000: yes, Denso also listing them as “C2A1535”, but then only later noticed that their projection is 1.5mm. And a video on youtube stating it should be 1.3mm. Spark Plugs and Coil Packs LHS Bank V21 Jaguar XK8 / XKR (X100) - YouTube
So, what to do? Was Denso’s spark plugs money wasted… haven’t installed them yet… Puzzled now what to do. Thanks a lot for good advices 
Welcome Matti, this is a screen shot from the AC Delco website as you can see they recommend 1.3mm f you have a set of feeler gauges then just re-gap the plugs down.
For further information regarding tightening the plugs I have included the URL as well;
Robin, thanks a lot for your kind help 
So, I measured Denso’s plugs, and faced new problem: is my tool having the right thickness… Once it showed only 0.9mm, I was simply too tired starting calibrating tools (i.e. buying a second one), so I just installed those Denso’s plugs. Felt that maybe Denso’s plugs like to be together Denso’s ignition coils (Jag factory original). Maybe there is not big difference is the projection 0.9…1.3mm, whatever…
Matti, what sort of tool are you using to check the plug gap?
Hi,
Just an universal tool, costs 4-5€/$
https://m.alza.cz/auto/merky-sparove-13ks-0-05-1mm-d5147190.htm?o=1
I am really sceptical is there at the end much difference between plugs, them, just using iridium, and that’s it.
Br, Matti