Tin-Plated Copper Tube, Polypropylene Sleeve, Ferrule Insulateds Insure reliable electrical connections and prevent fraying and breaking of wire strands when terminating conductors in screw clamp terminal blocks. Insulated ferrules have molded-on plastic sleeves and prevent conductor breakage due to bending, wire stress or vibration. Dual wire insulated ferrules provide reliable connection of multiple wires into the same terminal block clamp and simplify jumping between terminal blocks. All ferrules are packaged in 100-piece standard packs. Sleeve: Polypropylene.  Tube: Tin-plated copper.Ferrule insure reliable electrical connections when terminating stranded flexible wire in terminal blocks, circuit breakers or other control devices.Insulated Ferrule prevent conductor breakage due to bending, wire stress or vibration while facilitating wire insertion into the terminal clamp.