The Bach 36BO Stradivarius Series F Attachment Trombone is known for its flexible tone color and free-blowing feel. This is accomplished by using a .525-inch bore and traditional rotor with open wrap F attachment. An 8-inch one-piece hand-hammered bell gives the horn just the right amount of projection. The 36BO is available with a standard weight slide with a yellow brass bell (36BO) and gold brass bell (36BOG) or with a lightweight slide with a yellow brass bell (LT36BO) or gold brass bell (LT36BOG).