Rim inner diameter: 17.3mm Throat diameter: Approximately 4.0mm Cup depth: Medium - Material: Silver-plated - Type: French horn mouthpiece - Finish: Gold rim Thank you for viewing. This is a custom-made mouthpiece based on Willies' horn mouthpiece "PM," with a 17.3mm inner rim diameter, a deeper cup depth than the PM, and a gold inner rim. The use of a gold inner rim costs around 45,000 yen when new, so this is a more affordable option. Please consider it.