POM London Crochet Tam Beret Hat: Charcoal, Black Rim POM LONDON Handmade Unisex Tam Beret Hat Colour : Charcoal, Black Rim Size : One size fits all, stretchable (will fit 22" head up to 25" head) Material : Charcoal 25% Wool/75% Acrylic, Black 100% Acrylic How to measure your size. Using a tape measure, measure the widest part of your head, just above your ears and eyebrows.