Yamaha YTR-8330EM Bb TrumpetNew design leadpipe and mouthpiece receiver Thanks to just the right amount of playing resistance, high notes are easier to reach and overall control is notably improved. Step bore (ML) A step bore* (ML) design has been adopted to achieve optimum playability and tonal consistency throughout the instruments range. *The main tuning slide has an L bore, the valve slides have an ML bore, and the pistons have an M bore. This helps to maintain smooth,