The Proto J194 3 Piece Safety Wire Twister Pliers Set is made of hardened and tempered steel. Serrated jaws provide a firm slip resistant grip. The 0.020 in to 0.041 in and 0.020 in to 0.060 in wire sizes are perfect for locking down fasteners with twisted wires in aircraft and high-vibration machinery as well as on electronic connectors and coaxial cables used for TV signals and internet connections.