Gauges 10-13-17-26-36-46. Pure Blues electric guitar strings are designed with pure nickel wrap wire, roundwound upon round cores. While this is a slow, expensive method of string making, it does produce a string acclaimed for increased sustain, vintage tone, and great low tones for playing rhythm to lead. The extra step of winding pure nickel around a round core give Pure Blues strings a punch that players say they are surprised to get in a vintage string. Sounds great on any guitar!