4" compression electrical couplings are used to connect the ends of two 4” EMT thinwall conduits together to extend the raceway. Garvin Industries’ steel compression couplings provide concrete tight connections when taped, and are rated for electrical applications above 600 volts. Their heavy gauge steel construction maintains mechanical protection and solid grounding of one conduit to another. They are also zinc electroplated for excellent corrosion protection in damp locations.