Which type of conduit is described as having listed threaded or threadless fittings?

Rigid metal conduit is characterized by its robust construction and ability to provide excellent protection for electrical wiring, especially in environments where mechanical damage is a concern. The presence of listed threaded or threadless fittings is a significant aspect of rigid metal conduit, allowing for secure and reliable connections between different sections of conduit or with junction boxes and other electrical equipment.

These fittings create a tight, durable seal that helps in preventing moisture and dust from entering the conduit, which is crucial for maintaining the integrity of the electrical installations. Additionally, rigid metal conduit is often used in locations where physical strength and the ability to endure harsh conditions are essential, making it a preferred choice in industrial settings and outdoor applications.

The other options do not typically feature the same type of fittings or mechanical properties as rigid metal conduit. Non-metallic conduit, for instance, uses different attachment methods and is generally less robust. Flexible metal conduit, while it allows for movement and bending, does not usually utilize threadless fittings in the same way. PVC conduit is lightweight and resistant to corrosion but does not involve metal fittings, relying instead on solvent welding or other joining methods.