EB says:

Optimal For Detuning!

Ernie Ball Beefy Slinky Electric Strings are perfect for those who like to detune their instrument to lower tuning combinations.  Metal fans worldwide have gravitated towards the Beefy Slinky set to give their guitar the optimal gauge combination for Drop D & Drop C tuning. These strings are precision manufactured to the highest standards and most exacting specifications to ensure consistency, optimum performance, and long life. Beefy Slinky wound strings are made from nickel plated steel wire wrapped around a hex shaped steel core wire.  The plain strings are made of specially tempered tin plated high carbon steel; producing a well balanced tone for your guitar. Gauges .011 .015 .022p .030 .042 .054