The 820B Flamenco set has black nylon trebles and silver-plated wound basses. A great selling product over the years, the 820B is preferred by many flamenco players.- Bright Tone- Tension: Medium- String Gauges: Black Nylon: .028, .032, .040 Silver-Plated Wound: .028, .033, .041- Made in the USA with American Wire- Packaged using MAP Technology (Modified Atmosphere Packaging) to prevent tarnishing and ensure freshness