XO / JUPITER trumpet spring, barrel type. Barrel-type springs come in [strong] and [weak] variations, and this is the [weak] one. Although it says "for trumpet," it can of course also be used for cornets and 2-piece flugelhorns, and it seems to be usable on trumpets other than XO / JUPITER. Compared to the [strong] version, the spring force is a little lighter, making it ideal for those who want to play fast passages with less effort. I use this [weak] spring on all of my XO / JUPITER instruments. If anyone is interested, please let me know. Thank you. m(_ _)m I also handle other parts that can be used for various XO / JUPITER instruments. Please take a look if you'd like. (※The last photo is not included with this product.)