This mouthpiece is made of polished Sweet Iron which naturally oxidizes. About the mouthpiece: the 33 is the mildest Myler mouthpiece in terms of tongue pressure. The generously wide port allows room for the tongue to pass under the bit and swallow. Because this mouthpiece does not rotate on to the tongue and the port is wide, it applies little to no tongue pressure, working primarily off the bars, lips, chin and poll. The port on this mouthpiece is only 1 ½" high, so it will apply little to no palate pressure.