Instead of the usual hexagonal core, the Fender Classic Core strings feature a round core that forms the basis for a sound and feel typically found only in well-played strings. Right after stringing, you get a round, deep tone with smooth highs and a flexible string that makes even extreme bendings a real pleasure. Nickel Plated Steel Ball Ends. Gauges: .010, .013, .017, .026, .036, .046.