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Original Equipment was metal. Aftermarket can be either.
Some manufacturers reserve the right to change design and construction materials without notice. For example, a radiator listed as copper/brass may be supplied as plastic/aluminum, a radiator listed as 3 row may be supplied as a 2 row, or a radiator for a manual-transmission vehicle may be supplied with oil cooler fittings (which are unnecessary for a manual transmission but allow the same part number to be used for both manual and automatic vehicles). Regardless of design, the manufacturer offers the same warranty and the same assurance that the part will fit the vehicle application listed and perform as well or better than original equipment
Auto Mechanic
17 yrs experience and currently own and operate an Auto Repair Center