This is a BACH 3G mouthpiece for a medium-large shank. This rare item is a large shank BACH 3G that has been professionally modified to fit a medium-large shank. While large and small shanks are common on modern instruments, Besson euphoniums from about 50 years ago used medium-large shanks. Please note that this mouthpiece cannot be used with small or large shanks. There are scratches and plating wear from use. If you are interested, please bid. Please refrain from bidding if you are overly concerned about condition, as this item has been stored at home. Thank you.