This is my 4ply instarsia base teabag hat to fit newborn to adults. The fit is loose and slouchy, so if you prefer a tighter fit consider knitting one size smaller. 
 
I have also seen this style of hat referred to as a pussy hat when there are no pom-poms on the tips. 
 
This pattern includes written instructions on how to include my Instarsia charts on the front.
 
UK 4ply = US Sports =AU 5ply
Tention: 28 sts and 38 rows to 10cm, (4in) over stocking stitch on 3¼mm needles or the size required to give correct tension. Check your tension - if less stitches use a thinner needle, if more use a thicker needle.
 
Sizes
CIRCUMFERENCE
30cm, 34cm, 36cm, 40cm, 44cm, 48cm, 52cm.
Uses the circumference measurements for the most accurate sizing. Ages given in pattern are approximations.
 
Note the 52cm fits me but will stretch to fit a large head, it will just look less slouchy and more fitted. 

ID - Images show the largest size on the to and the smallest size on the bottom of the image