A plug (1) for use with a counterbalancing system (3) of a cable-operated door (5). The plug (1) includes flange and collar portions (13,15), the flange portion (13) being connectable to a mounting component (7) of the counterbalancing system (3) in order to allow a torque transfer from a torsion spring (9) to the mounting component (7), and the collar portion (15) being configured for winding into a given end (17) of the torsion spring (9), the collar portion (15) having opposite first and second extremities (19,21), and an outer surface (23) extending between these extremities (19,21), the outer surface (23) of the collar portion (15) being provided with a plurality of threads (25) and a plurality of corresponding recesses (27) each being defined between a pair of adjacent threads (25), each recess (27) being configured for receiving therein a single coil segment (11a) of the torsion spring (9), and being further shaped and sized for preventing another coil segment (11b) of the torsion spring (9) from embarking onto said recess (27).