Traditional wool berets come in one size, usually around a 56-57cm. However being good quality wool they can be stretched easily to fit your head and will stay the perfect size for you. This is easy to do:

1. Boil a kettle or pan of water until it is steaming
2. Grab your beret by the stalk on top
3. Hold it gently over the steam for a few seconds, being careful no to get your hands to close to the steam as it burns easily.
4. After a little steam, sit down and put the beret over your knee
5. Then put your fingers under the headband and pull firmly towards you, thus stretching the headband a little
6. Rotate the beret slightly and keep pulling towards you, repeat all around the beret.
7. Try it on, it should feel larger. If you need to make it bigger then repeat the above steps until its perfect
8. Your beret should stay this size forever (unless it ever gets really wet)
9. One tip, if your beret ever gets really wet it can shrink a little, so use this technique to restore it back to the perfect size.