These Helmholtz Coils from Eisco Labs consist of a pair of precision coils, each wound with 400 turns of copper wire on a former of approximately 150 mm diameter. The coils are mounted on a base with 4 mm terminals and can be positioned between 1.75 and 12 inches apart. The maximum current is 1 A to prevent overheating, and the direction of current is marked on each coil. Helmholtz coils produce a region of nearly uniform magnetic field between them when separated by a distance equal to their radius, making this apparatus suitable for experiments in electromagnetism and for calibrating magnetic field sensors in physics laboratories.