Since day one we have taken great care in making our coils. All Coil Cores are made from American Pure Iron (99.8% FE) specifically engineered for use in DC Electromagnets. Cores are individually faced to accurate size, and finished in Black Oxide for corrosion resistance. The cores are wrapped in a 3M Kapton film and then each one is hand wound with the finest copper magnet wire in house. . . Standard coils available 5/16” with an overall height of 1”.