Gauges 10-12-14-22-10. 80 20 bronze nickel wound. Martin M930 Nickel Wound Medium Bluegrass Banjo Strings combine rich deep bass strings with bright treble strings in specially matched sets to give bluegrass musicians the sound that discerning audiences appreciate. Bluegrass is one of America s finest musical traditions. C. F. Martin & Co. has been a part of this tradition for many generations with their legendary instruments and strings.