Boseno 10 Holes Double Tremolo Harmonica, Key of C (Blue) Imported phosphor bronze reed(Sound Spring):Copper content 99.99%,anticorrosion,antifatigue with brighter tone. Germany equipment:The Sino-German joint venture DMG CNC planer spring machine,guarantee the sound spring intonation. Thicken Copper plate,1mm copper plate makes the harmonica sound more clear and melodious. harmonica Cover design:thicken copper cover,fine printing design with enough hardness,it is not easy to deform with long time playing. harmonica use High quality ABS resin frets.Use Food grade ABS innocuity engineering resins frets,Waterproof and healthy.