A 6 3/4" MBB Black with Stainless Steel Dots Medium Shank with Sweet Iron Mullen Barrel Low Port (MB 06, Level 2 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.