Screw to adjust the idle mixture on the Solex ADDHE series carburetors.
This is the version with the coarse thread.
Please compare yours with the one in the photo to make sure it is the same version.
There is also a version with fine thread available.
The difference between the two is most clear in this photograph:
The overall length of this screw is 33.5 mm.
There is also a short, early version available.
You can find those versions on the general Solex ADDHE parts page HERE.
Required quantity per carburetor: 2
This is item number 15 in the drawing.