Circumferential and axial magnetizers for a magnetic flux leakage pig. A magnet bar may comprise at least one magnet and may be configured to collapse radially inward to the shaft. Magnetizers may include a cushion disposed about the shaft and biasing the magnet bar against a pipe wall. A sensor head disposed between circuit poles at each polar end of the magnet monitors magnetic flux. The central shaft of a circumferential magnetizer or axial magnetizer may comprise a joint linking an additional smart pig module. A novel magnetizer cushion is described, as are smart pigs containing one or more circumferential or axial magnetizers.