Alice Classical Guitar Strings (G-3 Wound) Concert Strings AC136BK-N Normal Tension (0.028 - .043), black nylon, nylon core, coated copper alloy wound, proprietary anti-rust coat, Mod. AC136BK-N US Nylon strings for classical guitar, normal tension (E .028, B .032, G .025, D .029, A .035, E .043). Black Nylon. Nylon Core. Coated Copper Alloy Wound. Proprietary Anti-rust coat.