The 520R "Red Card" Classical guitar string set from Savarez has been one of the most popular sets among Classical and Flemenco players thanks to the rectifying technology that produces treble strings with superior intonation. After having its gauge checked, each string is progressively and delicately modified to get a round shape throughout its length. These trebles are characterized by a distinctive unpolished finish. This grittiness contributes to a lessening of the high overtones, greater stability, and an ease of control over vibrato. The more traditional basses are warm and soft with a strong tone.