Ernie Ball Hybrid Slinky Flatwound Bass Guitar Strings, 45-105 Gauge (P02813) About this item Slinky Flatwound bass strings bring together the smooth feel of traditional flats with the power of Cobalt Cobalt alloy wrap wire delivers added clarity and output without the finger noise of a roundwound string Optimal core-to-wrap ratio ensures comfortable tension and playability Made in California, USA with the finest and freshest materials Gauges: 45, 65, 85, 105 Slinky Flatwound Bass Strings Ernie Ball Slinky Flatwound Bass Strings bring together the smooth feel of traditional flats with the modern power of cobalt. Cobalt, a metal that Ernie Ball introduced to the electric string world, displays a very strong attraction to the magenets in guitar and bass pickups. This enhanced magnetic relationship results in a flatwound bass string with increased brightness, clarity, and output without the finger noise of a round wound string.