Sticking the wire in white plastic case then insert the probe into the plastic case and pierce the wire.Will not damage the cables.prefect for back probing wheather pack styleThe Back Probe Lead Set has 3 different probe angles ( 90, 135, Straight),5 colors stainless steel back probes ,0.07mm needle ,testing up to 30 Volts for Connectors,Automotive Sensors and Fuel Injectors.The tail of the alligator clip can be connected to a 4mm male banana plug.5 colors for easy differentiation during testing. Maximum opening: 15mm. Current and voltage: 300Vac/15A.For automotive diagnostics, testing and repairing, also in physics laboratories, schools, homes and industries.Probes can insert into automotive connectors and use on harness connectors, fuel injectors and automotive sensors.Test wires length:39.37inchPackage Included:5pcs Banana Plug to alligator clip circuit test wires15pcs Wire Piercing Probes5pcs -plated copper Alligator clips5pcs Back Probe PinsColour:As ShownMaterial:PVC+copperPackage Contents:1 set probe 4Only the above package content, other products are not included.Note: Light reflection and different displays may cause the color of the item in the a little different from the real thing. The measurement allowed error is +/- 1-3cm.