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. Made for 5-string basses, this 50-135 Medium set has higher tension, affording increased low-end response and output.