Light strings for electric bassguitar. 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. Features set of four strings. String size: .040 / .060 / .080 / .100.