This is a Greg Black mouthpiece, loved by many professionals both in Japan and abroad. The 5GSD has a cup depth between a 5GS and a 5G, and is known for producing a rich, full sound from high to low tones. The lightweight design reduces the characteristic weight of Greg Black mouthpieces, improving playability. I acquired this mouthpiece used and used it for about a month, and I really liked it. However, it didn't quite feel right with my instrument, which is an older model, so I've decided to sell it. I plan to use the funds to purchase a new mouthpiece. Please check the photos for the condition.