Martin SP Flexible Core strings marry our thinnest core wire to our standard tensions. These Silk andamp; Phosphor acoustic guitar strings are made with bronzed steel core wire. Our SP Flexible Core strings feel soft to the touch, making them ideal for beginners. But don’t be fooled by comfort! Just ask Tommy Emmanuel who performs with our SP Flexible Core strings night after night. With SP Flexible Core, you get total flexibility and total control. Set: MFX130 Gauge: Custom 11-13-23-28-38-47 Tension: 128 Package: 6 strings