※ I have described price negotiations and other details in my profile. Please take a moment to review it beforehand. These are custom parts designed to modify a standard rotary tenor trombone, with the aim of enhancing its sound and resonance. This is the small size. We received feedback that the change in playing feel was quite noticeable when used, so we made this size with a slightly smaller outer diameter to reduce that change. The effect is somewhat reduced, but I believe the change in playing feel is also lessened. To use, simply remove the rotary cap, insert this part into the inner cap, and close the cap. It's easy to install and remove. This is made of copper, aiming to add a softer resonance. The diameter is approximately 19mm, and the hole is approximately 10mm. The thickness is approximately 0.3mm. It should fit most standard rotary instruments. (Please note that these are handmade, so there may be some variations and they are not perfectly circular.) While designed for use with trombones, it should also work with other rotary instruments like tubas and horns if they fit. (I have confirmed the sound change on trombones, French horns, tubas, rotary trumpets, and German tenor horns.) I believe it's possible to make some kind of change to an instrument, but it depends on the instrument and the player's compatibility, and the intended effect may not be achieved, or a completely different effect may occur. Please be aware that a positive effect is not guaranteed. Also, these are being sold elsewhere. We will prioritize the first person to purchase, so please understand. ps If you wish to purchase multiple items, please contact me. You can get a discount of 150 yen for each additional item, up to a maximum of 6 items. ※ The instrument used in the installation example is a V.Bach 42B. #FK Tone Disc Search terms: Trumpet Euphonium Tuba Bass