This is a thumb ring (made of stainless steel) for use on the tuba in St. Petersburg. This product allows you to bring your thumb about 10mm closer to the lever compared to the genuine ring, reducing the need to force your thumb, making fingering easier. The wider ring also helps to alleviate thumb pain. For those who find it difficult or undesirable to attach coins to the lever or have a repairman reposition the ring due to cost or appearance, this product is very convenient as it can be used immediately by simply replacing the original. Furthermore, this product features a skull motif design. If you like skull designs or want to make your instrument look cool, why not add a little flair to your instrument? Product Details: Inner ring diameter: 30mm, Wire diameter: 8mm Threaded part: M6 x 15 Material: Stainless steel Made of stainless steel, so it will not rust or have the plating peel off. ※ This product is a handmade item created by the seller. It may not be suitable for those seeking perfection, but it is a unique product that can only be found here, so we highly recommend it for those who appreciate originality.