Schilke ST30 Trombone - Yellow Brass Bell / Yellow Brass Hand SlideSchilke ST30 Trombone Yellow Brass Bell Yellow Brass Hand Slide The ST30 is Schilkes small bore tenor trombone. It incorporates a . 500 bore with a choice in both bell and hand slide material. Bells are 8 in diameter and offered in either hand hammered yellow or rose brass. The yellow brass bell affords the player a brilliant sound across the registers and is perfect for either lead or section playing, whereas the rose brass bell presents a warm,