I learn't a lesson with my current DIY project, try not to buy stuff from Bunnings if possible source from specialist places unless discounted heavily.
I bought some threaded rod from Bunnings 10mm x 1m cost $approx $8.00. Sound cheap. I went to Coventry Fasteners and bought a higher quality zinc rod for $3.80. Go figure
There are some specialist castor places may actually be cheaper, I know they have a much greater range.