Most men treat base layers as an afterthought and then wonder why they’re cold or uncomfortable the moment the temperature actually drops. The thermal detail is where it goes wrong most often. Either the fabric is too thin to do any real work, or it’s thick enough to be warm but looks ridiculous the moment a collar peeks above a shirt. We’ve been looking specifically at pieces that solve both problems at once. The thermal construction has to be functional enough to trap heat without adding bulk, and the collar and cuffs have to sit cleanly under whatever goes on top. Merino blends tend to win here because they regulate temperature properly and don’t hold odour the way synthetics do on a long day. Fit matters more than most people realise with base layers. Too loose and the warmth escapes. These are the ones we’d actually layer under a good shirt without thinking twice about it.