These track curtain hooks are made of high quality plastic, which is chemically stable, wear resistant, have good impact resistance and long service life. These curtain rail gliders won't stain your curtains due to rust compare to metal ones. Each curtain rail hook is specially designed to ensure an easy transition from track to track. The curtain gliders are high quality and offer effortless gliding through the curtain track sets. They make curtain opening and closing off more easily.