Greg Black 4G-5G Regular Trombone Mouthpiece. - Brand: Greg Black - Model: 4G-5G Regular - Type: Trombone Mouthpiece Thank you for viewing. I used this once for work, but it didn't suit me, so I'm selling it. My personal impression of the playing feel is that it has a very clear core and produces a powerful sound. I think it might easily overblow on a lightweight instrument. There are no major scratches, and it's generally in good condition. It's a used item, so please understand that it's non-refundable and non-returnable.