MINI DUCT HUNTER three/sixteen X 300′ The Mini Duct Hunter? features a copper trace wire within the rod for tracing or mapping inside smaller conduit or pipes. ? 3/16? rod diamter, 100? to 300? size ? Locate fiber optic cables in pvc pipe without tracer wire ? Works in 1/2? – 4? diameter piping. Longer lengths efficient in smaller diameter pipes or conduit.