Ferguson V Mouthpiece for Bass Trombone Size is approximately equivalent to a 1-1/2G. I am selling it because it no longer fits my instrument after I changed instruments. There are some areas where the plating on the inside of the rim appears to be peeling. Although this may vary from person to person, I was able to use it without any problems, and it did not affect the feel of the mouthpiece on my mouth or my grip.