A rotary feed-through designed to transfer a fluid between two entities, one of which is in rotary motion with respect to the other, said rotary feed-through comprising two coaxial cylindrical components, defined, respectively, as inner cylindrical ring (11, 11', 11") and outer cylindrical ring (12, 12', 12"), which are free to turn with respect to one another and are respectively provided with one or more inner channels and one or more outer channels for the passage of said fluid, each of said one or more inner channels and each of said one or more outer channels being connected via at least one annular space, each annular space being axially delimited by two seal rings (19, 19', 19"), said seal rings (19, 19', 19") being housed in a cylindrical seat of said inner cylindrical ring (11, 11', 11") or of said outer cylindrical ring (12, 12', 12"), said cylindrical seat facing respectively radially outwards or inwards and respectively being axially delimited on one side by an axial abutment made of a single piece with or coupled to said inner cylindrical ring (11, 11', 11") or said outer cylindrical ring (12, 12', 12"), and on the other side by an axial abutment of a lid (22, 22') coupled in a removable way to said inner cylindrical ring (11, 11', 11") or of a closing ring or of an intermediate ring, which are coupled in a removable way to said outer cylindrical ring (12, 12', 12"), said seal rings (19, 19', 19") being respectively interference fitted to said inner cylindrical ring (11, 11', 11") or to said outer cylindrical ring (12, 12', 12") and being provided with an elastic portion for contact with the surface respectively of said outer cylindrical ring (12, 12', 12") or of said inner cylindrical ring (11, 11', 11"); and said rotary feed-through comprising means that prevent the axial movement of said inner cylindrical ring (11, 11', 11") with respect to said outer cylindrical ring (12, 12', 12"), wherein at least one bearing (20, 20') is arranged between said inner cylindrical ring (11, 11', 11") and said outer cylindrical ring (12, 12', 12"), configured for supporting both the radial load and the axial load between said inner cylindrical ring (11, 11', 11") and said outer cylindrical ring (12, 12', 12"), wherein said inner cylindrical ring (11, 11', 11") is provided with at least one first shoulder (25A, 25C, 25') and said outer cylindrical ring (12, 12', 12") is provided with at least one second shoulder (25B, 25D, 25") that is arranged opposed to said at least one first shoulder (25A, 25C, 25'), wherein said at least one bearing (20, 20') is arranged between said at least one first shoulder (25A, 25C, 25') and said at least one second shoulder (25B, 25D, 25"), so that said at least one bearing (20, 20') constitutes at least one axial constraint in regard to the possibility of mutual axial sliding between said inner cylindrical ring (11, 11',11") and said outer cylindrical ring (12, 12', 12"), said at least one axial constraint being functional for maintaining the mutual position between said inner cylindrical ring (11, 11', 11") and said outer cylindrical ring (12, 12', 12") during mutual rotation, the rotary feed-through being characterized in that said cylindrical seat of said inner cylindrical ring (11, 11', 11") or of said outer cylindrical ring (12, 12', 12") is respectively axially delimited on one side by a first tab of said inner cylindrical ring (11, 11") or by a second tab of said outer cylindrical ring (12, 12', 12"), and on the other side by a tab of a lid coupled to said inner cylindrical ring (11, 11', 11") or by a tab of a closing ring or by an intermediate ring, coupled to said outer cylindrical ring (12, 12', 12").