It isn't just about flexibility; it's about bending the note till it rings true. Martin SP Flexible Core strings marry our thinnest core wire to our standard tensions. 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. Gauges: 013 017 026w 035w 045w 056w