Yamaha YAMAHA French Horn Mouthpiece HR-31D4 HR-31D4 Inner Rim Diameter: 17.28mm Throat Diameter: 4.50mm Features: This model has a larger inner rim diameter than the 30D4, and is characterized by a powerful, large sound. The rim shape is slightly flat with a moderate thickness, making it easy to play. Standard Series List Price: 6,380 yen (tax included) Please check the photos for details. Accessories such as the box are not included. Please understand that this is a used item before purchasing.