Dreamz Tunisian crochet hooks are made of polished birch wood & will work effortlessly with every type of yarn. They were designed by a team of artisans who know & understand the art of Tunisian crochet. Each size needle comes in a unique color for easy identification. The threaded, screw like system with tightening key will ensure that the needles never come loose when you are knitting. The smooth join ensures easy stitch glide with no snagging. In addition, the flexible cords will not kink or twist.