Abstract: Wire probes are described that resist rotation during assembly into a probe head of a die tester. One example includes probe wires with a protrusion at a pre-determined position along the length of the wire. A probe substrate with pads on one side each to attach to and electrically connect with a probe wire and a pads on the opposite side to connect to test equipment and a probe holder above the substrate with holes. Each hole holds a respective one of the probe wires against the probe substrate. Each hole also has a key to mate with a protrusion of a respective probe wire so that the protrusions engage the keys to prevent rotation of the respective wire.