XL ProSteels are D’Addario’s brightest bass guitar strings. The unique, highly magnetic alloy in ProSteels delivers super-bright tone with magnified presence and attack. Made with a high carbon steel core and stainless steel wrap wire, ProSteels produce enhanced interaction with magnetic pickups, offering a palette of harmonically rich, brilliantly penetrating highs, combined with pronounced, tight-and-tough lows. This 45-105 Regular Light Top/Medium Bottom gauge set has a great mix of tighter low-end with a comfortably balanced, bright top.