The PCWI COIL100 Circular Pipeline Coil Electrode 4" / 100mm Diameter # 0181 CPCE-0181 is ideal for verification of porosity or holidays on pipelines or circular surfaces. This PCWI circular Pipeline Coil is suitable for all High Voltage Porosity detectors, holiday detectors, spark testers and jeepers. The coil electrodes are shipped complete with ball bearing ends.