The EXP is D'Addario's entry into the coated strings market, and is one of their most sought-after strings. Their approach to coating strings is unique: They coat the wrap wire before it's wound around the base wire. This produces a string that maintains its response significantly longer than regular D'Addario strings (which is why coated strings are priced at a premium). The polymer coating also reduces string squeak. As with Elixir, several major guitar makers have begun to ship their guitars strung with EXPs because of their great, long-lasting tone.