IMC was developed in the 1970s as a "value engineering" solution for the electrical industry. It is a circular steel raceway that is thinner than Rigid Metal Conduit (RMC) but significantly thicker and stronger than EMT (Electrical Metallic Tubing).
It provides the heavy-duty protection of a threaded pipe system but weighs about 33% less than RMC. This makes it easier to handle, cut, and bend on-site.