Curt Mangan 10-56 7 String Electric Guitar Nickel Wound Set. Gauges: 10-13-17-26-36-46-56 String Length: 43 inches Nickel-Plated Steel wound strings were introduced in the late Sixties and have become the most popular alloy for electric guitars and bass. Nickel-plated steel tends to offer the most balanced tone. Nickel Wound strings are created by wrapping Nickel-Plated Steel alloys around a hex-shaped core wire which is made from tin-plated high-carbon steel (same as plain strings, but hex-shaped). The core-to-wrap ratio is the combined diameters of the core wire and the wrap wire which creates the overall diameter of the string.