The required dimensions of the connectors are:
This is determined by the damper manufacturer. In recent Rock Shox and Fox shocks, this is ½ "or 12.7 mm. Here then is sufficient to specify: "FOX shock".
This can be determined on the frame or the old bushes.
Note: Usually the installation widths above and below different.
Bolts / bolt diameter
This is usually 8 or 6 mm.
The outside diameter of my jacks is 18 mm.
The Bushes have always a bore diameter of 8 mm. For M6 screws then an adapter tube is included.
The sleeves are dimensionally matched to the plastic plain bearings, ie the original bearings do not fit in my sockets.