An internal combustion engine exhaust system includes an exhaust gas treatment unit carried at a carrier. The carrier has a receiving opening (20), receiving the treatment unit, with a first sealing surface (28) enclosing the opening. The exhaust gas treatment unit has a second sealing surface (42), enclosing a treatment unit longitudinal axis, located opposite the first sealing surface. The exhaust gas treatment unit has a third sealing surface (44), enclosing the treatment unit longitudinal axis. A closing element (48), fixable with the exhaust gas treatment unit to the carrier, has a fourth sealing surface (50), located opposite the third sealing surface. A first sealing element (52) is arranged between the first sealing surface and the second sealing surface. A second sealing element (54) is arranged between the third sealing surface and the fourth sealing surface. The first sealing element and the second sealing element are of identical configuration.