Yes sir - you are correct. Give you a little history/info. Factory BMW heat & AC parts have a mixture of copper & aluminum parts because they don't have access to the alloys here in the states (cost prohibitive) Any of them built here have the advantage. The two different materials expand & contract at different rates and usually if a leak apppears it's at a seam/soldered connection. That's why radiators can be a headache occassionally.