A coupling unit having at least one tubular section; a casing; at least one detent ring, which is arranged radially between the casing and the at least one tubular section when the at least one tubular section, is inserted in the casing, wherein the at least one detent ring, the casing, and the at least one tubular section are configured to adapt to one another such that the tubular section is inserted axially into the casing in a first relative rotational position of the tubular section and the casing, wherein the tubular section is secured by the detent ring against axial withdrawal, the casing and tubular section can be rotated relative to one another, and wherein for decoupling purposes, the tubular section can be withdrawn axially from the casing in a second relative rotational position of the casing and the tubular section that differs from the first rotational position.