These nuts are used to Bolt the Exhaust manifold to the head.
The studs and Nuts get affected by the amount of heat around the turbo manifolds- we recommend replacing them when you have the manifold off- as its a very painful exercise to have the nuts come loose after a short period or have the studs snap as you are tensioning them up.
The Thread size on these nuts is M10x1.5
Total width of flange is 21.5mm - in some applications this could foul
We also sell the Studs separately or in kit form for different models of vehicle- so search our other listings for these kits