The engineering design, the manufacturing methods and the magnetic measurements of the ion deflection magnets of the Joint European Torus (JET) Neutral Injection system are described. The magnets are ultra-high vacuum compatible, the coil being encased in a stainless steel jacket which incorporates a highly optimised water cooling system. High emphasis is placed on the reliability of the system. Magnetic measurements show adequate agreement with 3D computations and time dependent eddy-current computations.