Rod pole pieces can either be Alnico rod magnets or cylindrical carbon steel studs cut to the desired length and diameter. Steel stud pole pieces are basically used to direct the magnetic field from a permanent magnet within the components of the pickup. Rod pole pieces are normally non-adjustable and their length and diameter can determine the output from each string. As the studs are magnetized their proximity to the strings makes the string become magnetized. Normally the closer the pickup the greater the output and farther away the pickup becomes softer with less output. Alnico rod pole pieces are very typical in Fender style pickups and depending on the model pickup, various grades, diameters and length can produce a wide variety of tones and output.