What distinguishes RMC/IMC couplings from EMT couplings?

The distinguishing feature of RMC (Rigid Metal Conduit) and IMC (Intermediate Metal Conduit) couplings lies in their thread design. RMC and IMC conduits are constructed with a threaded end that allows for secure mechanical connections between the conduit sections. This threading is crucial as it helps ensure a tight fit, which is important for maintaining a secure electrical system and providing adequate protection against moisture and environmental factors.

In contrast, EMT (Electrical Metal Tubing) couplings do not feature threading. EMT is designed to be lightweight and is usually installed in a manner that emphasizes ease of assembly and handling, often using compression fittings instead of threaded connections. This difference in design and function is significant, as it directly impacts how each type of conduit is used in electrical installations.

Thus, the correct answer highlights the threading characteristic of RMC and IMC, which is essential in understanding their applications in conduit systems compared to EMT.