The invention is a highly flexible cable tie, comprising a head portion (T) and a tail portion (C), said tail portion (C) having one end (C1) joined to said head portion (T), said head portion (T) being provided with an opening (T1) for the passage of said tail portion (C) and with an elastic locking tooth (T2), said tail portion (C) being linear in shape, with generically rectangular cross section, and having on one longer side saw-tooth projections (C3) suited to be engaged with said flexible locking tooth (T2) of said head portion (T) and to prevent said tail portion (C) from sliding out of the opening (T1) of said head portion (T), said clamp having at least one projection (T3) on the wall (T1a) to which the flexible locking tooth (T2) is joined, said projection (T3) being suited to limit the bending of said flexible locking tooth (T2) towards the wall (T1a) to which said elastic tooth (T2) is joined. Said tail portion (C) does not have ribs, projections, raised lateral edges beside the saw-tooth projections (C3).