Yamaha Trombone Mouthpiece Gold Plated Large Shank 48A brass instrument mouthpiece is much more than an add on or accessory. It is a vital part of your instrument. As interface between artist and instrument, it can mean the difference between mediocrity and mastery. GP Series (Small Shank, Large Shank) GP Series has been created especially for professionals who require superior quality from their mouthpiece. The GP Series features an innovative shape and extra heavy gold plate finish for players who