This connects to the leaf springs

 

I would guess it is a metric bolt by the hardness markings on it .

 

put some wrenchs on it & see...I'd guess 12, 13, or 14 MM.

 

I'm pretty sure it's an 18mm. I vaguely remember that from removing my rear sway bar.

 

Me, too.

 

could be......pic is kinda deceiving..................I just remember the sway bar itself is really small in diameter

 

The bolt head is 18mm.

As for the thread size and pitch, who knows?

Those pieces just go in the scrap metal pile when I remove the rear sway bars.

 

don't people use those brackets as bar pin eliminators?

i always throw mine out too.

 

18 mm. But it's an deep socket though. At least for the other side that isn't in the picture. I used an adjustable wrench to stop the bolt shown in the picture from spinning while I loosened the bolt on the other side.