Daddarrio Ej13 80/20 Bronze Acoustic 011-052 Ej13 Is A Custom Light Gauge 80/20 Bronze Set That Features Lighter Top And Bottom Strings For Ease Of Playability And Balance. 80/20 Bronze, The Original Acoustic Alloy Introduced To By John D’Addario Sr. And John D’Angelico In The 1930S Is A Popular Alloy For Recording Due To Their Crisp, Deep And Projecting Tone And Appeal To Many Traditionalists And Vintage Enthusiasts For Their Historical Significance.