A guitar string has a ball end made to anchor in a guitar bridge. Most mandolin and banjo tailpieces have hooks or pins made for loop end strings, so a ball end usually won't seat properly.
Even if you could make one fit, the gauges wouldn't be right. A mandolin is tuned G D A E in fifths on a short scale with paired strings, and a 5-string banjo has its own tuning and a short 5th string. Guitar gauges are chosen for a different scale length and different pitches, so the feel and balance would be off.
Use strings made for the instrument:
- Our mandolin sets (M1036PB, M1140PB) are 92/8 phosphor bronze and loop end.
- Our banjo sets are stainless steel and loop end, for 5-string, tenor and plectrum banjo.
If you break one string, our specialty singles include loop end plain steel, mandolin phosphor bronze and banjo wound strings, so you can replace just that string.