Technical Top strut mount nut size?

[scott9951]

As the topic says what size and grade is the top nut on the strut thanx?

 

[John202020]

Which one? There's actually two nuts at the top, the one you can see looking under the bonnet and the larger one that holds the top mount and spring cup and spring under compression?

 

[scott9951]

Which one? There's actually two nuts at the top, the one you can see looking under the bonnet and the larger one that holds the top mount and spring cup and spring under compression?

The top one that gets rusty

 

[Jockstrap]

Why?
My replacement struts came with top nuts.

 

[Mike1alike]

Exterior is 19mm hex size. The thred pitch is fine, I don't know the exact pitch, I think is 1.25.