Acoustic Science NiSt 9's Premium Treated Nickel Steel X-Light Guitar Strings, 9-42 Guitar Strings - Gauges 9-42, Premium Nickel Steel for your Martin, Dean, or Fender electric guitars. Made In USA - Nano-thin polymer surface treatment applied to every string. Minimal breaking-in time- Low surface energy maintains sound quality. Longer Lasting - High tech nanotech surface makes it easy to play right out of the bag. Microscopic non-stick surface - State-of-the-art technology for best possible sound - Hex core finest wrap wire.