A 6 3/4" MBB Black with Stainless Steel Dots Medium Shank with Sweet Iron Wide Ported Barrel (MB 16PB, Level 3) Copper Inlay. This mouthpiece is made of polished Sweet Iron which naturally oxidizes or rusts. Harmless to horses, it has a sweet taste and promotes salivation. Black shank will discolor over time to an antique brown. Stainless steel dots.