DDT™ Drop Down Tuning Electric Guitar Strings maintain their intonation at lower tunings thanks to Accurate Core Technology™ (ACT™), a coated hexagonal core wire that locks the nickel-plated steel wrap wire in place to increase stability and maintains intonation at any tension. DDTs go right into tune and deliver clean and clear notes. Change tunings and be surprised how DDT's lock right in without constant adjustment. Accurate Core Technology™ (ACT™) was developed to reinforce the core wire and fill in imperfections along its entire length. Superior core wire is recognized as the foundation for rich tone, accuracy of intonation and durability.