Black Beautiesâ„¢ acoustic guitar strings with K3â„¢ Technology The K3 coating is the first coating that players report, "sound as good or better than uncoated strings." DR's remarkable and proprietary K3 Technology coating is the first coating that makes no apologies and no excuses for not delivering sound equal to uncoated strings. Players tell us that these strings have more volume, less unwanted overtones, greater clarity and articulation than standard, uncoated strings. Yet, they provide the same protection due to corrosion and perspiration as well as increased tone life that coated strings are known for. <> String Length: 38" <> Material: K3 Black Coated Phosphor Bronze. Hexagonal Core Wire with Ball End. <> 13 17 26 34 45 56