The Bach 36BO Stradivarius Professional Tenor Trombone is a perfect instrument for the player looking for a Medium-large bore trombone. The Bach 36BO features a .525" bore and a one-piece hand hammered bell for increased resonance. With an open wrap F attachment, the 36BO is available with a yellow brass bell (36BO), gold brass bell (36BOG) or with a lightweight slide with a yellow brass bell (LT36BO) or gold brass bell (LT36BOG).