Choosing the right track or pole can make a huge difference to the look of your window. Typically choose a track when it will sit behind the curtain, or top-fixed into a recess, while a curtain hanging down below a pole can make a real statement of style, especially with a plain curtain and a contrasting pole.
The most common pole sizes - poles that are 20-30mm in diameter. Suitable for all but the heaviest curtains.