D'Addario EXPs deliver the most natural-sounding, longest-lasting coated strings available. Through their advanced EXP Coated Technology, D'Addario have perfected the art and science of coated string-making to deliver extended play strings that sound identical to their world famous XLs. Plus, they have dramatically improved the corrosion resistance, longevity and durability of plain steel strings through an exclusive compound tin-plating process. Finally...coated electric strings that deliver longer life, completely natural tone and the feel of uncoated strings. You won't believe they are coated!