What is the purpose of the metallic donut?

[ISAslot]

When I got my enlight 7237 I noticed that there is a metal disk with the led/power wires looped through. What is the purpose of this?

 

[BA]

It's a choke, to reduce noise in the lines. But for an LED, I don't really think it's all that necessary, but as long as it's on there, might as well leave it alone.