They are made of aluminum and are with a satin finish.
Dual Carb 4150 6-71 8-71 Blower Adapter Plate Polished
Speedmaster Dual Carb 4150 6-71 8-71 Blower Polished Adapter Plate
Speedmaster Dual Carb 4150 Blower Adapter Plate For GM 6-71 10-71 Superchargers
Dual Carb 4150 6-71 8-71 Blower Adapter Plate Polished Finish w/ Hardware