Accu-fret fretwire is manufactured from a nickel/silver alloy, sometimes called German silver. The 6S6290 wires are 18% which refers to nickel content. The 65S6290 are "hard" wires. “Hard” and “Soft” refer to how malleable the fretwire is: hard fretwire is more difficult to shape and is better suited to large radius or flat, classical fretboard; soft fretwire is easier to shape and is more suited to small radius fretboards. Dunlop Accu-fret fretwire is also available in brass and 18% nickel content in soft condition, and 12% nickel content in both hard and soft conditions, offering a tremendous array of fretwire for luthiers worldwide.