Crown Hat BlockLightweight multi use hat block for straw and raffia braid hat forming, not wool hat blocking. To determine your head size, and which block to order, run a flexible tape measure around your head where a hat would sit. Across the forehead and including the "ball" of the back of the head. If the number is a fraction go with the next size up. The average womans size is 22, Children's is 19 20. Sizes 19 23 circumference.