"An acoustic string that retains is brilliance for much longer period, due to the phosphorous content. Phosphor bronze strings also produce a longer sustain than plain bronze strings. Popular for acoustic Rock, Country, Folk, Bluegrass, or just about any style of acoustic gutiar playing. The "E" in "EJ" stands for environmental version. We support the environment, and so should everyone. They are the same strings as thier regular packaged phosphor bronze, except in an environmentally friendly package. They have done away with the plastic wrapping, and minimized packaging waste by 75%. "