System for storing and discharging a flowable multi-component composition, comprising: - a coaxial cartridge having a hollow-cylindrical cartridge inner wall, and a cartridge outer wall which is arranged coaxially around said inner wall and is cylindrical at least on the inside, and having an inner chamber for a first component that is delimited radially by the cartridge inner wall, and an outer chamber for a second component of the composition that lies radially between the cartridge inner wall and the cartridge outer wall, as well as having a cartridge front wall which firmly closes the two chambers (6, 7) on an end face of the cartridge and has a discharging opening in each chamber; and - a support structure which is designed to receive and hold the cartridge when the composition is pressed out of said cartridge and for this purpose has a side wall which is shaped at least partly like a tube portion and is at least partly closed on its first end face by a support structure front wall designed to support the cartridge front wall; - wherein an inner diameter of the side wall is varied or can be adjusted in the axial and/or radial direction of the support structure in such a way that an annular gap between the cartridge outer wall and the side wall is created or can be adjusted when the cartridge is inserted into and removed from the support structure, and a tight fit of the side wall against the cartridge outer wall is created or can be adjusted over the duration of a pressing-out process, characterized in that the cartridge outer wall is also cylindrical on the outside; - the side wall of the support structure is designed as a cylindrical tube which is slit in the axial direction; and - the support structure has an externally operable closing and opening mechanism for this slit such that, when the slit is open, the tube has an inner diameter which is larger than an outer diameter of the cartridge outer wall by a predetermined double annular gap width, while, when the slit is closed, the tube fits tightly against the cartridge outer wall. - a coaxial cartridge having a hollow-cylindrical cartridge inner wall, and a cartridge outer wall which is arranged coaxially around said inner wall and is cylindrical at least on the inside, and having an inner chamber for a first component that is delimited radially by the cartridge inner wall, and an outer chamber for a second component of the composition that lies radially between the cartridge inner wall and the cartridge outer wall, as well as having a cartridge front wall which firmly closes the two chambers (6, 7) on an end face of the cartridge and has a discharging opening in each chamber; and - a support structure which is designed to receive and hold the cartridge when the composition is pressed out of said cartridge and for this purpose has a side wall which is shaped at least partly like a tube portion and is at least partly closed on its first end face by a support structure front wall designed to support the cartridge front wall; - wherein an inner diameter of the side wall is varied or can be adjusted in the axial and/or radial direction of the support structure in such a way that an annular gap between the cartridge outer wall and the side wall is created or can be adjusted when the cartridge is inserted into and removed from the support structure, and a tight fit of the side wall against the cartridge outer wall is created or can be adjusted over the duration of a pressing-out process, - the side wall of the support structure is designed as a cylindrical tube which is slit in the axial direction; and - the support structure has an externally operable closing and opening mechanism for this slit such that, when the slit is open, the tube has an inner diameter which is larger than an outer diameter of the cartridge outer wall by a predetermined double annular gap width, while, when the slit is closed, the tube fits tightly against the cartridge outer wall.