Before the late 60's, pure nickel was the only option available for guitar strings. It gives a more vintage sound which is ideal for blues, jazz, soul and early rock'n roll. The feel is a little sloppier so you can choose the next size of strings for a fuller sound or stay with what you had an experiment easier string bends. Note that you will have to adjust your treble settings on your amp because they are less bright than modern strings, so you have to compensate to cut thru the general mix in a band. Will give you a warmer sound easily.