Martin FX745 light-medium phosphor bronze acoustic guitar strings use a thinner core wire to deliver greater player control with sharp attack, increased flexibility and improved harmonic sustain. The wrap is constructed of 92/8 bronze and the core wire is Martin's platinum: high carbon steel with special zinc flashing. Recommended for acoustic rock rhythm styles.92/8 Phosphor Bronze This alloy is comprised of 92% copper, 8% tin and traces of lead, iron, zinc and phosphor. These strings produce a bright but slightly warmer sound than the 80/20. The phosphor in the alloy helps them to retain their new sound for greater consistency in brilliance levels.Platinum High carbon steel with special zinc flashing that gives the wire better tensile properties. Martin uses platinum on the FX string sets to increase the durability and improve harmonic sustain.It has been said that the guitar becomes a mini orchestra when played fingerstyle. In fingerstyle's simplistic form, the thumb is setting the beat and the fingers are working through the melody. While that sounds rather basic, it is rather challenging to master. Despite all the instruction and guidance on fingerstyle playing, very little focus has been given to the string where the sound is truly initiated. So, Martin started from scratch in their string research facility and worked with several fingerstyle groups to develop a string that would be more responsive to fingerstyle methods. After creating many samples in the lab and working with the fingerstyle groups, they determined that a fingerstyle string should deliver crisp, clear notes with little overtone and light sustain. The string needs to be flexible and almost soft to the touch, but very controllable. And, since fingerstyle playing is not a forceful style, the string needs to deliver the proper resonance and vibration to the top to create the right volume.The end result: Martin FX Flexible Core, available in 80/20 Bronze for maximum brilliance out of the box, and 92/8 Phosphor Bronze for warmth and consistent brilliance. The silvered steel plain strings provide the traditional tone and longevity you expect from Martin. The zinc flashed thinner core wire and thicker wrap wire increase the resonance and control while creating a more flexible string. Ultra-pure high tensile strength steel has been chosen to maximize the durability of the string. Martin asked a member of the Michigan Fingerstyle Guitar Society to give them his feedback on the Martin FX strings. Here is Dave Wodnicki's experience: "The new Martin FX strings are truly a great set of wires. On the sound, the tone is clear/warm and they ring very nicely. On the feel, great to the touch but what I really noticed was that when I played up above the 7th fret all the way up to the 14th, it took less effort to make the chords, runs and bass lines. I was able to move around a bit easier and the control was very solid, which means I had plenty of reserve energy for expression