Cap / Hat stretcher enlarger for big Heads

I designed this ting because I always had the problem with too tight caps for my big head...

Hardware you'll need:

1x M8 stop nut (or use threadlockable)
4x M8 nut
2x M8 washer
1x threaded rod cut to the size you'll need for your head
1x M8x25 nut (a simple nut will do the job too, but its more guided with the long one)

If you like this thing, I like coffee ;)