The original idea was to use 1 inch plastic curtain rings, but it turned out they were 20 for £5, which is ridiculous. I can't afford £130 for curtain rings. So instead, I have the flexible plastic rings from around the neck of the bottle my daily yogurt drink comes in. It's a pain trying to snip off spiky bits on them, but it has to be done. Then I crochet around them so they look nicer and any rough bits left on the rings are covered. As of tonight, I have 200 mostly done. I just need to weave in the yarn ends.