Off the Ideal packaging card that these come with it states AL & CU... It also indicated the size/quantity of conductors here are acceptable... (Bill looked on a card for me
) I'm hoping this was just a sloppy homeowner splice that wasn't done too well as I've used these purple wirenuts alot of times! The HO already had the device pulled out of the box & stated he had shut the breaker off... I touched the twisted AL's with my hotstick & they arc'ed! One for test before you touch!