Size F/5 (4.00mm) Crochet Hook.
Finished Size: Approximately 13in/33cm deep, but the bag is very stretchy.
From the author:
Made with colored plastic string, available in hardware or stationary stores, this string bag is very inexpensive to make and easy to work. Make several in different colors, filled with colorful plastic toys to hang next to the nursery bathtub. Alternatively, hang them in the pantry, and fill them with fruit and vegetables. Work alternatives in natural twine or leather thonging, fill with seashells and driftwood, and hang them in the bathroom.