Gives your arm a more comfortable contour and also helps to protect the top of the guitar from perspiration. Most importantly, it allows you to play normally while it lifts your arm clear off the top of the guitar, giving you all the sound your guitar has to give.The outer edge of the John Pearse Armrest is a compound curve so that it can conform to a wide variety of body shapes. It is attached to the surface by means of a double-sided adhesive strip, developed to hold it securely without harming the delicate lacquer of the soundboard. If you have a guitar that has a high value as a "collectable", you may want to reflect on the addition of an Armrest because it is not considered "Original Equipment."The John Pearse Armrest is designed as a permanent addition to the guitar - as is a pick guard or a bridge.