Ernie Ball Super Slinky RPS Nickel Wound Electric Guitar Strings - 9-42 Gauge. A patented winding of brass wire is tightly wrapped around the lock twist of the ball end of the plain strings. String slippage and breakage are minimized at the ball end where these most often occur. Plain strings in RPS sets last longer and stay in tune better than conventional plain strings. Ernie Ball s RPS wound strings consists of specific gauges and core to wrap ratios for balanced rich harmonics and that signature Slinky feel. Ernie Ball Slinky gauge combinations today s industry standard were pioneered by our founder Ernie Ball more than 50 years ago helping shape the sound of rock n roll.