I made these using a 4mm crochet hook and two lengths of double knit (so that it became a chunky wool).

They came out bigger than I expected, but are cute and they can be grown into.

Had a few problems, where I had to undo it a few times, but once I got these problems ironed out they made up quickly and look cute once the button is added at the end.

Have a look at my other projects over at my blog:
http://surfjewels.tumblr.com/