Eyelet curtain typically comes with a large ring embedded in the curtain. The rings may be plastic or made of metal. Each comes with pros and cons. There are many types of metals used in ring form Brass to sheet metal. Brass rings last and gives a superior look whereas the sheet metal rings look like budget curtains. Rings made of metal cannot be removed from the curtain. Hence it is not a good choice.
Plastic rings come in many colors and ranges in quality. Plastic rings of good quality are recommended over metal rings for many reasons. Firstly, the color of the ring can be closely matched with the curtain fabric shade. Second, it can be removed during washing or dry cleaning and can be put back easily. Care has to be taken when the rings are removed from the curtain. The punched hole in the curtain should be handled with care. Otherwise, fabric thread will start coming out of the hole and the hole will enlarge. Put back the eyelet rings at the earliest. Thumb rule for the fabric requirement is 50% of the fabric will get consumed in the pleats. Check out the design here.