D'Addario EXPs are the most natural-sounding, longest-lasting coated strings available. EXP Coated Technology starts with the highest quality wrap wire materials, precision drawn and micro coated on our advanced proprietary machinery. Strings are then wound normally, delivering tone and feel identical to D'Addario's world renowned XL line of bass strings, with a minimum of 4 times more life. You won't believe they are coated.