Ernie Ball Super Slinky Classic Rock n Roll Pure Nickel Wrap Electric Guitar Strings - 9-42 Gauge. Classic Rock’N’Roll strings consist of pure nickel steel wrapped around a tin plated high carbon steel core for a warm rich tone that compliments many playing styles including jazz, rock and blues. Each set is packaged in an ultra low humidity environment with Ernie Ball’s element shield packaging to ensure every set is as fresh as the day it was made.