Our silver wound Classits with a ball on the end of each string. We have developed a process to have the ball end fastened more securely to the string. Gauge: D-4TH Package: 1 Single String S.I.T. ( Stay In Tune )… It is our goal that you will always be in tune if you are using any of our products. S.I.T. Strings was founded on a belief that a guitar string is more than just an accessory of little importance, but rather an integral part of a musicians sound and voice. That is why, since 1980, we have been manufacturing strings one at a time, all here at the S.I.T. Strings factory in Akron, Ohio USA.