Fluid connection unit (10, 110), which is adapted to connect a fluid line not belonging to the fluid connection unit (10, 110) to a further fluid line, also not belonging to the fluid connection unit (10, 110), wherein the fluid connection unit (10, 110) comprises a neck portion (14, 114) which is adapted to be inserted into the fluid line and which has a nominal outer diameter, wherein at least one sealing element, in particular an O-ring, is arranged on the outer circumference of the neck portion (14, 114), which sealing element is adapted to bridge a distance between the fluid connection unit (10, 110) and the fluid line when the fluid connection unit (10, 110) is connected to the fluid line and thus to seal the connection with respect to an outside, wherein the fluid connection unit (10, 110) comprises a protective element (22, 122) which is arranged on the outside of the neck portion (14, 114) so as to be displaceable from an initial position on the neck portion (14, 114) to an end position, and which comprises a substantially cylindrical portion at least on its radially inner side, wherein the at least one sealing element in the initial position is radially outwardly overlaid by the cylindrical portion of the protective element (22, 122), wherein the cylindrical portion of the protective element (22, 122) has an inner diameter which substantially corresponds to the nominal outer diameter of the neck portion (14, 114), wherein the cylindrical portion of the protective element (22, 122) is adapted to receive the fluid line to be connected on its outer side, and wherein the fluid connection unit (10, 110) further comprises a calibration portion (26, 126) which is arranged at a free end of the neck portion (14, 114) and which has an outer diameter (44, 144) that decreases towards the free end of the neck portion (14, 114), characterised in that the maximum outer diameter of the calibration portion (26, 126) is greater than the outer diameter of the cylindrical portion of the protective element (22, 122) adjacent thereto in the initial position. wherein the fluid connection unit (10, 110) comprises a neck portion (14, 114) which is adapted to be inserted into the fluid line and which has a nominal outer diameter, wherein at least one sealing element, in particular an O-ring, is arranged on the outer circumference of the neck portion (14, 114), which sealing element is adapted to bridge a distance between the fluid connection unit (10, 110) and the fluid line when the fluid connection unit (10, 110) is connected to the fluid line and thus to seal the connection with respect to an outside, wherein the fluid connection unit (10, 110) comprises a protective element (22, 122) which is arranged on the outside of the neck portion (14, 114) so as to be displaceable from an initial position on the neck portion (14, 114) to an end position, and which comprises a substantially cylindrical portion at least on its radially inner side, wherein the at least one sealing element in the initial position is radially outwardly overlaid by the cylindrical portion of the protective element (22, 122), wherein the cylindrical portion of the protective element (22, 122) has an inner diameter which substantially corresponds to the nominal outer diameter of the neck portion (14, 114), wherein the cylindrical portion of the protective element (22, 122) is adapted to receive the fluid line to be connected on its outer side, and wherein the fluid connection unit (10, 110) further comprises a calibration portion (26, 126) which is arranged at a free end of the neck portion (14, 114) and which has an outer diameter (44, 144) that decreases towards the free end of the neck portion (14, 114), characterised in that the maximum outer diameter of the calibration portion (26, 126) is greater than the outer diameter of the cylindrical portion of the protective element (22, 122) adjacent thereto in the initial position.