100 PK Dottie RC3 3/8″ Steel Rod Coupling – Threaded Connector for Rods 100 PK Dottie RC3 3/8″ Steel Rod Coupling – Threaded Connector for Rods The Dottie RC3 is a 3/8″ steel rod coupling designed to join threaded rods in electrical, HVAC, and plumbing installations.