Does Anyone Know What The Little Round Piece Does

Thank you

It the ferrite for use on a thru bolted application...

Thank You

You asked what it does, Faztbullet said it is a "Ferrite". The word Ferrite triggered a response knee jerk reaction from me since I am having coffee, nothing to do, forgetting more of what I used to know than I originally knew type thing and trying to hand on to a little of it.

Besides it's usage as indicated, have no idea as to that, in general electronic circuits, Ferrites are usually ceramic material that is magnetized and can be slipped over wires (power supply wires in particular) to control high frequency interference...example would be you have ignition static on your marine radio caused by the engine's spark plug firing system. The long wires from the engine to the Helm provide a good antenna for picking up noise such as that or other things running that radiate interference.

Slipping a suitable Ferrite over the noisy wire will absorb/block the noise while allowing the DC voltages to pass unobstructed, as would be the case if a resistor or induction coil were placed in the line to limit the receiver noise/static.

I'm chasing down a potential electrical problem and I kept seeing those pieces in pictures of coils and couldn't figure out where they went. Unfortunately I found out that the 2 piece ferrites that go over the coil are real brittle and break super easy.

Being a compressed ceramic powder, if of the type I agree.