Horn Mouthpiece Pressure Release Valve

Purchased on Amazon in July 2025. I am selling it as I do not use it very often. It is almost unused, but there are some scratches from moving inside the included case. These were present from the time of purchase.
The retail price was 6,789 yen.

The following is quoted from the Amazon product description:

Daconovo French Horn Mouthpiece Pressure Relief Valve Breath Trainer - Mouthpiece Pressure Reducer to Correct Excessive Pressure on French Horn

This is an excellent tool to monitor your pressure usage, adjust your breathing, correct incorrect playing methods, and help you play in the correct way.
Precision CNC precision carving and careful design make playing easier.
It allows you to adjust the pressure according to your skill level, resulting in easier playing and a more accurate, better sound.
Made of high-quality brass material with gold/silver plating on the surface, it is very durable and has a smooth and beautiful appearance.
The nozzle pressure relief valve is suitable for French horns and is easy to install and use.