DDT™ (Drop Down Tuning) Electric guitar strings lock in at even the lowest tunings, thanks to DR's Accurate Core Technology™. Coating the hexagonal core wire increases tuning stability and maintains intonation at any tension by helping lock the nickel-plated steel wrap in place.  Accurate Core Technology also extends the life of the string by creating a barrier against dirt and sweat between the core and the wrap wire.  Now you can drop lower and change tunings often with pitches that are clean, clear and rock solid!