Small (Measures 1 5/8” Tall X 2” Wide)
Medium (Measures 2 1/4” Tall X 2 1/2” Wide)
Large (Measures 3” Tall X 3 1/2” Wide)
Extra Large (Measures 3 1/2” Tall X 4 1/4” Wide)
Jumbo (Measures 4 1/2” Tall X 5 1/2” Wide)

There IS a gauge swatch included in the pattern for those that have specific sizing requirements. I use an F hook in the pattern. This will work with any worsted weight yarn. It will also work with sport weight or lace if you lower your hook sizing, note if you do this, your skull will be smaller than the pattern says.

Pattern is simple to follow and has photo tutorials for the only difficult spot.