An electrical fitting in the form of a connector or coupler for connecting an electrical metallic tube or EMT to an electrical box or panel or to one another. A unidirectional locking device is disposed in an outermost chamber and an O-ring is disposed in an intermediate chamber. The unidirectional locking device has gripping tangs. The intermediate chamber and gripping tangs are sized so as to prevent the gripping tangs from contacting the O-ring. A contact shoulder is used on one end of the fitting to prevent excessive compression of a sealing washer. Internal longitudinal radially increasing ribs are formed in the fitting body improving continuity and support for the EMT. A tube support may also be provided to prohibit any undesirable bending movement of the EMT connected thereto.