9/16 x 3.5 Inch Greasable Shackle Bolt suits most common for use in 45mm eye to eye or shackle springs with steel bushes.
Measure from the tip of the bolt to under the head of the bolt for the correct length.
Shackles bolts both greasable and non-greasable should not be so tight they squeeze or pinch the spring. Tighten just enough to leave about .5mm gap each side.
This allows the spring to flex up and down with the expansion and contraction of camber.
If you draw a line from eye to eye and measure down to the spring from the center of this imaginary line, this is your camber measurement. It can flex up to 40mm during the normal driving cycle.
So you can see it is important not to over tighten your springs.
9/16 = 14mm
9/16 x 3.5 Inch Greasable Shackle Bolt