Hat shown is ladies small. You can make hat larger by casting on more stitches in multiples of 4.

Stitch patterns used in this pattern are mentioned in the Pattern Post here:
http://smariek.blogspot.com/2006/11/striped-slip-stitch-hat.html
and also in the Pattern Bibliography post here:
http://smariek.blogspot.com/2007/11/pattern-bibliography.html
.