The Bach 1-1/2G trombone mouthpiece is one of the most traditional mouthpieces for the bass trombone. It has a large shank with a medium-sized throat and backbore, meaning that it is not a heavy, "full-sized" bass trombone mouthpiece (like the Bach 1G or the 1-1/2GM), but rather a "light" bass trombone mouthpiece with a "symphonic tenor" throat and backbore, producing a relatively bright bass trombone sound. Its rim is thin and rounded, offering great flexibility. The rim diameter is large and requires a good amount of air and embochure strength, but not so much as a full-sized bass trombone mouthpiece.
all in all, it is a great mouthpiece for the student or small bass trombone player, with a beautiful bright sound.