This is a Grieggo lightweight tenor trombone mouthpiece, size 4.5. It has a thin gold plating. I bought it to match my European trombone, but it's surprisingly versatile and also works well with Yamahas and other brands. The inner diameter is 25.65mm, but due to the rim shape, it feels slightly more compact, so I think users of the 5G will have no problem using it. In fact, in terms of overall balance, it might be easier to play than a 5G. It's easy to handle with its light weight, but it's not weak and can still produce a solid volume. It's likely to suit those who: - Like the stable 5G type with its deep resonance and well-controlled sound. - Want the delicate, bright, and clear articulation of Brahms pieces with that character, but desire a bit more freedom. - Find heavier American-style mouthpieces a bit too hard-sounding and want something with a softer tone, but still want to be able to blow powerfully when needed. - Want a versatile mouthpiece that they don't need to switch out. Currently, a new Grieggo mouthpiece costs a little over 30,000 yen, and even a thin gold plating adds over 20,000 yen (a normal thickness gold plating would add around 60,000 yen, which is scary...). So it's become quite a luxury item... *Price negotiation is okay, but if you request it, please try commenting with an interesting story related to the product or music, a helpful tip, or your passion and enthusiasm. I will discount it based on how much it resonates with me. If you only present an amount with no comment, I will close the request. (´ー｀) This is to prevent resellers.