A plumbing fitting includes a housing defining a socket with an internal annular shoulder for sealably receiving a cartridge. A two-piece cylindrical cartridge has semi-cylindrical interlocking halves that lockably engage a grab ring positioned between the interlocking halves of the cartridge. The grab ring has inwardly projecting annularly spaced tines for gripping and holding a fluid conduit inserted into the housing and cartridge past the grab ring. The cartridge includes a ring seal positioned against the annular shoulder and internal wall of the socket for sealably coupling the cartridge to the socket and sealably coupling a fluid conduit to the cartridge. The cartridge may be held within the housing socket by a crimped-over end. Also, an integral release ring may be coupled to the cartridge, such that a separate tool is unnecessary to disconnect a fluid conduit from the fitting.