Warwick M4 EMP Coated Bass strings feature Enhanced Molecular Protection - a unique micron-thin coating that protects your bass strings against corrosion. EMP Bass strings feel like an uncoated set of strings, yet last much longer. Now you can have a long-lasting bass string with the tonal output and feel of an uncoated bass string. One Micron. That's all that stands between you and your bass guitar's tone.