Depending on the make and model wind turbines are mostly made of steel, about 66-79% of total turbine mass. Fiberglass or plastic makes up about 11-16%. Iron or cast iron make up 5-17%. Copper only makes up about 1% and aluminum can make up to 2%. Many of the wind turbines’ parts are manufactured right here in the United States. Wind turbines are 60-75% domestically sourced. Blade and hub parts are 30-50% domestic. Nacelle assemblies are over 85% domestically sourced. Many of the wind turbines’ internal parts such as pitch and yaw systems, bearings, bolts and controller type parts are usually imported from other countries (“What Materials”).