All 36 series Bach Stradivarius tenor trombones feature .525" medium-large bore, 8" one-piece yellow brass bell, chrome-plated nickel silver seamless inner slide, brass outer slide, nickel silver handgrip, tubular nickel silver body braces, genuine Vincent Bach mouthpiece, deluxe wood shell case. The Model 36BO features; Key of Bb/F, F traditional rotor mechanism, open wrap.