Made in the USA since 1907, Gibson strings use only premium US materials and vacuum pack each package for freshness. Standard on all Gibson guitars, Gibson strings feature proprietary cover-to-core ratios for sweet feel and tone, and have a hex core of Swedish steel for awesome response and sustain. These strings are also slow-wound using Gibson"s special Tension Release system for optimal tone. Gibson"s QC is second-to-none, ensuring consistency from set to set, and they offer their strings in a variety of materials and gauges, giving your guitars a wide tonal spectrum.