XL ProSteels are D’Addario’s brightest electric guitar strings. The unique, highly magnetic alloy in ProSteels offers a super bright, crunchy tone, and increased sustain. Made with a high carbon steel core and stainless steel wrap wire, ProSteels produce enhanced interaction with magnetic pickups, creating an extraordinarily bright tone that will cut through any mix. This 9-42 Super Light gauge set is easy to bend and very flexible.