YAMAHA French horn mouthpiece 29D, metal, with case. - Brand: YAMAHA - Model: 29D - Material: Metal - Accessories: Case Thank you for viewing. I purchased this here. I used it before and bought it again, but it doesn't suit my current instrument, so I'm selling it. It's discontinued, but it's a double cup, and I think it might be good for those who feel that the current Yamaha 30D4 (the mouthpiece I currently use) takes in too much air. The backbore is unknown, but it feels similar to a 30C4.