Worst strings ever, received them, opened them up and tried to unroll the loop to put on YOYO. This took about 20 minutes. do. With great determination I finally succeeded. I'm 71, found my old Ducan YoYo. I've been doing this for many years. Polyester material (which I've never used, bad choice, this material has a memory, unlike cotton. YoYo WILL NOT ROTATE SO YOU CAN'T DO TRICKS, MIND, it just moves up and down but that's it. Waste of money !