Long Island Brass Pollard Sarastro Aria 900 Inner Rim Diameter: 29mm Throat: 0.312in Backbore: B2 This is a bass trombone mouthpiece. I purchased it a few months ago and used it a few times before storing it. There are slight scratches from use, but it's almost like new. The threads move smoothly and can be removed. The Obligato backbore and cup, which I am selling separately, are compatible and can be exchanged. In my personal opinion, both the Aria and Obligato felt larger than other companies' mouthpieces of the same size, perhaps due to the rounded rim. I usually imagine that rounded rims make the sound blurry, but perhaps because of the V-cup-like shape, the articulation was rather clear. It had a crisp yet rich sound with a lot of resonance, a tone I'd never experienced before. When I played it alone, I thought it was for solo use, but surprisingly, it was easy for others to play with, which was unexpected. Also, the overall length is supposed to be longer than a standard mouthpiece, but for some reason, the pitch is higher than other companies' mouthpieces of the same size. Compared to the Obligato, the Aria feels easier to control and more compact to play, with the sweet spot being closer. Please consider this opportunity. Sarastro Aria The solo model Sarastro Aria achieves a beautiful and diverse palette of tones while maintaining tonal consistency throughout the entire range of the bass trombone. By combining the "DNA" of the standard series mouthpieces with the new EON design, the Aria model achieves unprecedented tonal diversity and control across the entire range. This allows the player to freely "shape" the sound in solo performances and express their musical ideas more richly. Moreover, it does not compromise the overall tone. B2 Backbore The second most open of the three bass trombone backbores. In the owner's Instagram photos, this backbore was paired with the Aria, so I ordered them together. I also sent a photo of Pollard to Long Island Brass and confirmed, so I believe there is no mistake in the combination.