Heavy Formvar magnet wire is copper wire with a thin layer of insulation, and is used mainly in winding guitar pickups. Raw copper is drawn to meet specific size requirements based on the National Electrical Manufacturer's Association (NEMA) standards. This magnet wire meets the NEMA MW-15-C standard for operating temperature (105°C/211°F) and insulation makeup. The insulation is made from a Heavy Formvar enamel, and protects the coiled wire from short-circuiting.