Bill Rusk asked for a weight comparison in a previous thread
Stripped Cast Aluminum Covers -- 29.3 oz for four.
Powder Coated Cast Aluminum Covers -- 29.6 oz for four.
Powder Coated Stamped Steel Covers -- 22.8 oz for four.
The Stamped Steel ones are 6.8 oz (23%) lighter which makes sense since aluminum weighs one third of steel of the same thickness but the aluminum ones are more then three times the thickness of the stamped steel ones.
I still like the aluminum ones!
Submitted by the Weights & Measures Division of Starr Aero.