Just to prove what a great collection of hat patterns this is, this book has already sold out in the first print run after just one day. Thirteen designers fill this book with fifteen ace hats. Hats are just such fun to knit; quick, small, portable and an easy size to finish. Quick gratification! Always useful, they finish an outfit off and apart from keeping you warm they are great on a bad hair day. These will work with any 4 ply yarn.