GP/MR-200 heavy build magnet wire is the standard of comparison for magnet wire performance in virtually every severe and heavy duty application. The combination of a modified polyester basecoat and an improved polyamideimide topcoat results in an insulation system with outstanding physical toughness, excellent dielectric properties, and superior chemical resistance to most common solvents and refrigerants. - Windability of GP/MR-200 heavy build magnet wire, verified by years of experience on virtually every type of winder, has always been excellent. Improvements in the topcoat have resulted in a product that is even more superior with regard to high slot fill and insertability. GP/MR-200 magnet wire is classified as 200 °C on copper conductor and 220 °C on aluminum.