Industrial Coupling Acouplingconnects two pipes. If their sizes differ, the fitting is known as areducing coupling,reducer, or anadapter. There are two types of couplings: "regular" and "slip". A regular coupling has a small ridge or stop internally, to prevent over-insertion of a pipe, and thus under-insertion of the other pipe segment (which would result in an unreliable connection). Aslip coupling(sometimes also called arepair coupling) is deliberately made without this internal stop, to allow it to be slipped into place in tight locations, such as the repair of a pipe that has a small leak due tocorrosionorfreezebursting, or which had to be cut temporarily for some reason. Since the alignment stop is missing, it is up to the installer to carefully measure the final location of the slip coupling to ensure that it is located correctly.