A protective bellows, comprising, in combination: - a plurality of flexible annular elements made of polymeric material having an inner edge (D2I) and an outer edge (D2E) and connected, in use, in succession along a direction of extension of the bellows, one of the flexible annular elements defining a first end of the bellows, another of the annular elements defining a second end of the bellows and the remaining flexible annular elements defining a central region between the ends (E1, E2), each of the flexible annular elements being sealed to another flexible annular element adjacent to it in a first sealing region close to the inner edge (D2I) in such a way that each of the annular elements and another flexible annular element are connected together close to their inner edges (D2I), - at least one diaphragm having an inner edge (D4I) and an outer edge (D4E), - at least one supporting element for supporting the diaphragm having an inner edge (D5I) and an outer edge (D5E), interposed between a pair of flexible annular elements of the central region, the diaphragm being connected, in use, to the supporting element for being carried by the supporting element, the protective bellows being characterised in that it further comprises: - at least one stiffening element, having an inner edge (D3I) and an outer edge (D3E), interposed between a pair of flexible annular elements of the central region in such a way that the flexible annular elements of the pair are sealed on the stiffening element at a second sealing region close to their outer edges (D2E); and in that - the at least one supporting element is interposed between the pair of flexible elements of the central region in such a way that the flexible annular elements of the pair are sealed on the supporting element at a second sealing region close to their outer edges (D2E), the supporting element being equipped with at least one protrusion defining, in use, a fixing surface and configured for protruding, in use, beyond the outer edges (D2E) of the flexible annular elements. - a plurality of flexible annular elements made of polymeric material having an inner edge (D2I) and an outer edge (D2E) and connected, in use, in succession along a direction of extension of the bellows, one of the flexible annular elements defining a first end of the bellows, another of the annular elements defining a second end of the bellows and the remaining flexible annular elements defining a central region between the ends (E1, E2), each of the flexible annular elements being sealed to another flexible annular element adjacent to it in a first sealing region close to the inner edge (D2I) in such a way that each of the annular elements and another flexible annular element are connected together close to their inner edges (D2I), - at least one diaphragm having an inner edge (D4I) and an outer edge (D4E), - at least one supporting element for supporting the diaphragm having an inner edge (D5I) and an outer edge (D5E), interposed between a pair of flexible annular elements of the central region, the diaphragm being connected, in use, to the supporting element for being carried by the supporting element, the protective bellows being characterised in that it further comprises: - at least one stiffening element, having an inner edge (D3I) and an outer edge (D3E), interposed between a pair of flexible annular elements of the central region in such a way that the flexible annular elements of the pair are sealed on the stiffening element at a second sealing region close to their outer edges (D2E); and in that - the at least one supporting element is interposed between the pair of flexible elements of the central region in such a way that the flexible annular elements of the pair are sealed on the supporting element at a second sealing region close to their outer edges (D2E), the supporting element being equipped with at least one protrusion defining, in use, a fixing surface and configured for protruding, in use, beyond the outer edges (D2E) of the flexible annular elements. - at least one stiffening element, having an inner edge (D3I) and an outer edge (D3E), interposed between a pair of flexible annular elements of the central region in such a way that the flexible annular elements of the pair are sealed on the stiffening element at a second sealing region close to their outer edges (D2E); and in that - the at least one supporting element is interposed between the pair of flexible elements of the central region in such a way that the flexible annular elements of the pair are sealed on the supporting element at a second sealing region close to their outer edges (D2E), the supporting element being equipped with at least one protrusion defining, in use, a fixing surface and configured for protruding, in use, beyond the outer edges (D2E) of the flexible annular elements.