ZEBRA acoustic-electric strings are wound with a mix of nickel-plated steel wire and RARE phosphor bronze wire alternatively – every other coil is nickel-plated steel, every other coil RARE phosphor bronze! They are designed for acoustic-electric guitars with Piezo pickups under the bridge or magnetic pick-ups in the sound hole. Full-size Archtop Jazz guitars also respond to the Zebras with richer tones according to players. ANY amplified acoustic comes ALIVE when you put on the Zebra strings. Revolutionary because no one has ever done this before. And no one else does it yet. It is the very first string where you can SEE the difference.