Expansion connectors (joints) are fittings that allow for longitudinal movement to provide expansion, and contraction when connecting rigid metal conduit to a junction box. This may happen for a variety of reasons such as when conduit is entering a foundation, from ambient temperature fluctuations, from unintended consequences of long conduit runs, or building design requirements. Made by Crouse-Hinds, OZ Gedney and others, they come in sizes ranging from 1/2" to 6" and are available as a coupling or a connector. The connectors offer a possible advantage over couplings in that the maximum amount of movement possible is limited only by the space in the junction box. Given that rigid connectors allow for up to 4" or 8" movement, this feature can be an advantage.