Guage is not important.
Smaller hooks will create a smaller beanie, larger hooks and heavier yarn will create a slightly larger beanie.

This pattern is written in US terminology.
Do you have a few scraps and a few minutes to spare for charity?
Could you make a few of these teeny tiny beanies for charities?
Australia:
Little Angels Memory Boxes
https://www.facebook.com/LittleAngelsMemoryBoxes

USA
Calvins Hats
https://www.facebook.com/calvinshats

UK
Lisa’s Stars
https://www.facebook.com/pages/Lisas-Stars/159738440713941