Product review (4 stars): This blade is designed to rotate on a square shaft ...
This blade is designed to rotate on a square shaft and chop (crush) ice. I'M not sure what the metal is, possibly aluminum, but over time the center of this part wears to point where the shaft rotates without turning the blade. Since it's not very expensive, I guess that is to be expected. The problem is when you call a repair man to fix the ice maker and the price of the service call is way more than the cost of the part.