Piano back rail cloth (key cloth), used to replace the worn out felt underneath the back of the piano keys. High quality dark green cloth, the strip measures 1.5" in width by 52" in length, and is .185" thick. When installing, it is recommend that you glue under the front edge of the felt, but not the back edge (the part of the key that comes down on the felt). This will give you a softer sound, and the option to shim under the felt if so needed.