IF i remember correctly thread is M10x1,25. Aldo not sure right this moment. M10 is for sure
I have bought few years back headles nuts that was adverted as "renault gordini fit" but they did not fit.
Thread was alright but had to redone taper at late machine to 45°
And original one are 17mm hex spaner.
My headles nuts are also 19mm hex.
They fit, so no need to bother about that.
You can ask seller what is taper on this nuts.
Do not mention that they are for renault wheels