I have used cotton that is suitable for a size 3 hook, but you can use any type of yarn and hook as long as they fit each other. I would love to see your finished dumbbells so please share photos of your finished items! Here comes the boring but necessary part: Copyright: Please respect my copyright. Feel free to make as many items as you like from this pattern. However it has taken me a long time to design and test each of my patterns, and then translate them from Danish into English, so please don(tm)t copy, sell or distribute the pattern itself. If you wish to sell the finished item, please include the following credit: Crochet pattern designed by Kirsti Testroote, www.ByKirsti.dk. This should be mentioned on any card or label supplied with the finished product. If you sell online you should include a link, to Ravelry were the pattern can be bought, along with your description. Thanks again!