Bass set in medium tension from the 550MT set 2x D4, A5, and E6. Calibrated strings made from the finest materials produce a homogeneous, powerful tone with great projection. The Professional series allows solo artists to fully explore the sound possibilities of their instrument. An extra D4 string is included in the bass set. The silver-plated winding wire of the bass strings (nylon-silk core) features a special surface treatment that prevents tarnishing and discoloration over time. The strings are spun under pre-tension, allowing them to quickly hold their tuning after being strung.