Myler Flat Shank Correctional MB 27Stainless Steel 7" Flat Shank, MB 27 Correctional Level 2 3 The MB 27 is a traditional correctional mouthpiece, which has a ported mouthpiece that collapses on to the outer lip and bars, and rotates on to the tongue. This mouthpiece has a 2" port and is identical to the MB 27PB HP, except that it does not have Independent Side Movement. Sweet iron mouthpiece oxidizes and encourages salivation. NO Independent Side Movement Sweet Iron Mouthpiece Curved