Beta-matrix compositor
From Memory Alpha, the free Star Trek reference.
The beta-matrix compositor is a component of Cardassian plasma distribution manifolds, which cannot be replicated.
In 2373, the plasma distribution manifold of Deep Space 9 needed to be repaired, but the beta-matrix compositor could not be replaced by Starfleet. Thus, Chief Miles O'Brien led a salvage team to DS9's abandoned sister station Empok Nor. (DS9: "Empok Nor")
