This is a BestBrass Groove 6B GP mouthpiece for tenor trombones. It is new. To embody BestBrass's image of a "wonderful trombone sound," this mouthpiece has a moderate weight but features a design that concentrates weight in the rim. Trombone mouthpieces with weight concentrated in the rim provide an unprecedented balance. Groove TB-S-6B Rim Inner Diameter: 25.375mm Cup Depth: Slightly Deep Throat Diameter: 7.1mm Backbore: TB-M Comparable to: Schilke 50 This model is one cup depth deeper than the TB-S-6C. It is characterized by a soft tone and is popular not only for trombones but also for euphoniums.