This reel of bare Eureka (constantan) wire is a copper-nickel alloy with a low temperature coefficient of resistance, making it suitable for resistance coils and precision electrical experiments. The wire is 24 SWG (0.55 mm diameter) and supplied on a reel of 125 g. The low temperature coefficient means the resistance remains relatively stable across a range of temperatures, which is an important property for constructing standard resistors and for experiments where consistent resistance values are required.