EPS510's offer a super-bright, crunchy tone and corrosion resistance for longer string life. D'Addario XL ProSteels utilize a highly magnetic, corrosion-resistant steel alloy that delivers super-bright tone without shrill overtones. They offer a palette of harmonically rich, brilliantly penetrating highs combined with pronounced, tight-and-tough lows. If you're looking for more crunch, bite, and sustain, ProSteels are the choice for you.