A tube coupling (10) which includes a tubular, electrically conductive housing (11), a seal (12) for sealing against the outside of a tube, a substantially annular and electrically conductive grab ring (13) for gripping the outside of a tube and an annular cartridge ring (15) between an inner surface of the housing (11) and the grab ring (13). The cartridge ring (15) includes a projection (30) that projects radially inwardly and is positioned so that upon insertion of a tube into the tube coupling (10), an edge of the grab ring (13) bears against the projection (30) and the cartridge (15) bears against a facing surface of the housing (11) to provide electrically continuity between the grab ring (13) and the housing (11).