Device for storage and delivery of a liquid and/or gaseous medium under pressure comprising: a medium-holding medium container made of a plastic material, preferably polyamide, at least a valve connecting element connected with the medium container, at least a valve element (3, 3a, 3b) that can be connected with the valve connecting element, wherein the medium container is integrally formed with a collar protruding from the medium container and having a collar outer wall and a collar inner wall, wherein the end of the collar defines the free cross-section of an opening of the medium container, wherein the valve connecting element is arranged in the area of this opening, while a section of the collar outer wall is arranged opposite a section of a wall of the valve connecting element, and wherein the valve element (3, 3a) has a pressing section which lies opposite a section of the collar inner wall in the assembled state of the device, wherein between the section of the wall and the pressing section, there is, in addition, at least a restoring element (11, 11a, 11b) that is so arranged that, upon assembly of the valve element (3, 3a), the collar and the restoring element (11, 11a, 11b) are pressed together between the section of the wall and the pressing section, wherein the restoring element (11, 11a, 11b) is made of a cross-linked plastic material, preferably cross-linked polyethylene, and wherein the pressing section, the collar and the restoring element (11, 11a, 11b) are so matched and formed that the joint pressing of the collar and the restoring element (11, 11a, 11b) causes an elastic deformation of the restoring element (11, 11a, 11b), which is larger than the maximum creep deformation of the collar over the service life of the device, so that the creep deformation of the collar is compensated by the restoring element (11, 11a, 11b) and a permanent press fit is created between the pressing section, the collar, the restoring element (11, 11a, 11b) and the section of the wall, characterised in that the restoring element and the collar are sleeve-shaped and plugged into or plugged onto one another, and the pressing section is enclosed by the restoring element and the collar, wherein the outer diameter of the pressing section is larger than the inner diameter (d) of the collar and/or the restoring element before assembly of the valve element (3, 3a). a medium-holding medium container made of a plastic material, preferably polyamide, at least a valve connecting element connected with the medium container, at least a valve element (3, 3a, 3b) that can be connected with the valve connecting element, wherein the medium container is integrally formed with a collar protruding from the medium container and having a collar outer wall and a collar inner wall, wherein the end of the collar defines the free cross-section of an opening of the medium container, wherein the valve connecting element is arranged in the area of this opening, while a section of the collar outer wall is arranged opposite a section of a wall of the valve connecting element, and wherein the valve element (3, 3a) has a pressing section which lies opposite a section of the collar inner wall in the assembled state of the device, wherein between the section of the wall and the pressing section, there is, in addition, at least a restoring element (11, 11a, 11b) that is so arranged that, upon assembly of the valve element (3, 3a), the collar and the restoring element (11, 11a, 11b) are pressed together between the section of the wall and the pressing section, wherein the restoring element (11, 11a, 11b) is made of a cross-linked plastic material, preferably cross-linked polyethylene, and wherein the pressing section, the collar and the restoring element (11, 11a, 11b) are so matched and formed that the joint pressing of the collar and the restoring element (11, 11a, 11b) causes an elastic deformation of the restoring element (11, 11a, 11b), which is larger than the maximum creep deformation of the collar over the service life of the device, so that the creep deformation of the collar is compensated by the restoring element (11, 11a, 11b) and a permanent press fit is created between the pressing section, the collar, the restoring element (11, 11a, 11b) and the section of the wall, characterised in that the restoring element and the collar are sleeve-shaped and plugged into or plugged onto one another, and the pressing section is enclosed by the restoring element and the collar, wherein the outer diameter of the pressing section is larger than the inner diameter (d) of the collar and/or the restoring element before assembly of the valve element (3, 3a).