I don't know what it is actually called, actually.
I talked to Apple Chat support though and I still don't know what to do.
Edgar:
Correct that really is there to protect the product during shipping and can be removed. Its not a vital component to the charger. the charger should work fine without. In my experience we do not ship or replace those plastic sleeves.
Me:
Even if my mac is still under warranty?
Edgar:
Absolutely, just to clarify again since it is under warranty you can absolutely take that charger in and ask them to look at that and see about replacing the plastic shipping sleeve. From what I understand its mean’t to protect the metal during shipping and is not a permanent protective sleeve. Does that make sense to you?
Me:
Yes.