One-size beret - How to enlarge it?

Have you bought a one-size Basque beret and don't know how to adjust it to your head size?

It's very simple, you hold it by the inner rim and stretch it between your hands.

If that's not enough, you can use your knee to stretch it with your hands by gently pulling it towards you.

Here's a very comprehensive video from the French beret specialist, Laulhère, explaining it: