The original bushes for this location (including proprietary Spas ones) are simple cylindrical rubbers with a steel sleeve; they protrude only very slightly from the eye at the bottom of the shock.
For some reason, some aftermarket 'poly' bushes are formed in two 'top hat' halves that push in from either side over a similar metal sleeve, meaning there is a lip beyond the eye as per Phil's photo'.
Phil is correct that these plates would be of greater interest to those who've fitted after market 'poly' bushes with the lip, but my concern here is that a gap will be left between the plates and the ball joint casting, which would need packing with washers of the appropriate size to stop the ball joint being able to wander 'fore and aft, despite being fixed in place by the vertical link...
The replacement plates are the same thickness as the originals.
So no packing of washers or shims are needed.
All it’s doing is giving extra support to the lower Shock Bush.
Unless the lower shock Absorber sleeve is too long resulting in excess gap.
Easier to trim the sleeve.
Yes my Spax have two piece bush’s as the original Spax rubber bush’s just don’t last.