Z-motor/rod coupler for A8 and I3 compatible. Tight fit to reduce/remove Z wobbling on the axis. 5mm stepper shaft to 8mm threaded rod, attach via M3 screws & nuts left over from the printer assembly.
Tolerances are 0.2mm so if you don't want to have to hammer it in place, make sure your printer can print somewhat decently.
I hope it helps, let me know if it fixed your Z-wobble!