Clarinet thumb rest cushions simply slip on over the metal rest for added comfort whilst playing. Treat your thumb today! The BG thumb rest cushions are designed so you can choose the thickness of the padding available to you. This is done by making the slit for the metal rest concentic, so the thickess of the padding will vary depending on which way round you choose to fit it. BG cushions also come in two sizes as the size of metal or plastic thumb rests varies. If you are unsure which size you need you could always buy one of each as they are not expensive.