Specfication:This acoustic are wound automatically with foreign hexagonal cores and Phosphor Bronze alloy Wound. With the mature anti-rust techniques, the long-life strings offer crisp and tone.Coated SteelHexagonal CoreCoated Copper Alloy WoundE-1st Coated Steel:0012 inch / 03mmB-2nd Coated Steel:0016 inch / 041mmG-3rd Coated Copper Alloy Wound:0024 inch / 061mmD-4th Coated Copper Alloy Wound:0032 inch / 081mmA-5th Coated Copper Alloy Wound:0042 inch / 107mmE-6th Coated Copper Alloy Wound:0053 inch / 137mmColor:as shownMaterial: copper alloyPackage Contents:1 Set of Strings6pcsOnly the above package content, other products are not included.Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.