D’Addario was the first to use Phosphor Bronze in acoustic guitar strings back in 1974 and eventually expanded the alloy to include acoustic bass strings. Today, Phosphor Bronze is played throughout the world and considered to be the standard in acoustic strings, thanks to its beautiful sonic balance and tonal warmth. Phosphor Bronze acoustic bass strings are precision wound with phosphor bronze wrap wire over a high carbon steel core, providing tonal versatility suitable for most acoustic bass styles. Made for 5-string acoustic basses, this 45-130 Regular Light 5-string set fits most standard sized acoustic basses.