Nickel Plated Steel is a wire used in quality musical strings. Because of the nature of the alloy, NPS has a little smoother outside feel. It also has a special kind of "Growl" that some people refer to. Full of tone and a great feel, Helix NPS is one of the great bass strings in the Helix Bass line. Helix NPS Bass features a patent pending design and construction. Just like the SS Helix Bass, NPS Bass features the Hyper Elliptical Windings (compressed from side to side), which gives Helix more Mass and Tone, as well as extended life. This Hyper Elliptical winding is what gives Helix its special feel-a more relaxed feel, with a lot less squeak and sliding noises than normal strings.