A ferrite material in which Bi2O3 is added at 6% by weight or less, and preferably 4% by weight or less, to a ferrite of Li\u2014Zn\u2014 containing a specified amount of Mn. The shoulder attachment system includes a first and second shoulder strap individually coupled to the external surface of the enclosure member. The connective port connects electrically to a host machine. This allows the wheel diameter to be changed for application to various types of vehicles. An apparatus for performing the method is also provided.