Abstract: A method to use an RFId (Radio Frequency Identification)-identifier for recognition of roll ware, such as a roll of paper or like, whereby an RFId-identifier is being exploited that is to be placed essentially in connection with a core and which includes a transponder, being formed at least of a RFId-microcircuit and an antenna. For recognition of roll ware, a RFId-identifier is being used that is to be placed in connection with the core and that exploits a magnetic field, existing essentially uniformly all over the same in a radial direction. Also provided is an arrangement applying the method.