Universals in travel. The men's driving cap. See it here at Vlad's castle ruin in Romania, worn by The Guide.
Many of us know little of the stitcheries of driving caps vs. newsboys' caps, and other similar caps around the world. The fashion is global because it is practical, the cap is easy to carry, stays on, and looks good.
Sometimes there is a buckle in the back. The longer the brim in front, the tougher the look. This fine guide, who lives near the ruin, was gentle and had a welcoming cap.
Measuring for a driving cap. What is your size? For a European cap, measure your head, say in inches for Americans, then multiply that times 2.54; or, for an American cap, divide by 3.14 or pi.