[ILLusion]

It keeps the grub screw from contacting the motor shaft.

You MUST have this, if you want to:

1) Maintain correct motor height
2) Prevent burning out your motor
3) Prevent burning out your fuse
4) Prevent very loud motor noise
5) Prevent burning out your battery
6) Prevent melting your wires

!!!

So in short..... yes, it's a big deal.