I am selling this item because I am retiring. I used it with a Troy's bass trombone. Inner diameter 28.00mm, Bach 1G equivalent size. I selected and purchased this from three of the same model when I bought it. It seems to be a discontinued model now. There are some minor scratches from use, but it is in relatively good condition. Please judge the detailed condition from the images. No returns, no refunds, no exchanges (3N) strictly enforced.