Trumpet Atelier Tsubasa 4CS Mouthpiece

Trumpet Mouthpiece, Atelier Tsubasa 4CS.
This is a beautiful item, only tried once.
It's like a Bach 3C, but with a slightly smaller inner diameter while maintaining the same cup depth.
Here is the official description:

Original Trumpet Mouthpiece 4CS

This mouthpiece is made by slightly reducing the inner diameter of the original trumpet mouthpiece 3CS.

With Bach mouthpieces, when moving to smaller sizes than 3C (like 5C or 7C), the cup depth increases, making it difficult to achieve the brilliant and radiant tone of the 3C. However, by keeping the 3C depth and making the size slightly smaller, it becomes easier to play in the higher registers while retaining the 3C's tonal quality.
It is also recommended for students with smaller physiques.

It was created with the goals of smooth blowing feel, smooth transitions across all registers, good responsiveness, and maximum resonance efficiency with minimal effort.

~Specifications~
- Rim:
The semi-flat shape of the MV 1-1/2C made by Mr. Kameyama, loved by musicians worldwide regardless of professional or amateur status, is maintained. The inner diameter has been adjusted to be slightly smaller than the 3C size. This shape balances stability and controllability.

- Cup:
Modern 3C depth, producing a bright and brilliant tone.

- Throat:
#27 (φ3.66mm)

- Backbore:
Modeled after the backbore of a specific Bach 3C that had clear intonation and a natural resonance (Bach #10).