Fair Isle Hat Pattern with Latvian Braid - includes 2 sets of charts to make hat to fit head sizes: 24.5, 23.5, 22.5, 21.5 inch head size. Half an inch for ease means hats are:

21” & 22” hats use size 5 & 6 needles
23” & 24” hats use size 6 & 7 needles

Based on BBC’s Sherlock series - ‘The Wallpaper Had It Coming’ scene