These strings are as "vintage" as you can get. Pure nickel wrap on a round tin-plated, high carbon steel core. Many players believe that round core strings feel easier to play with less tension and have a clearer tone. By design, round core strings must be handled carefully so that the outer winding does not come lose. On guitars that have an eye in the tuning post, it is important to install the string and tune to pitch before cutting the excess string off. On guitars where the tuning post has a hole down the center which require the string to be cut prior to placing the string down the post hole, it is important that you first make a 90 degree bend before cutting the string. It best to make that 90 degree bend about two inches longer than the post where you will be installing the string. Once you have made the bend leave about one-half inch before cutting the string then place the bent section inside the tuning post and tune to pitch. Be aware that it takes longer for a round core strings to "settle" in and it requires many more tugs, but once installed and settled in, they are amazing.