Smartwool is probably best known in the UK for its range of merino wool socks, but the brand also produces merino clothing including this 220-weight, winter-friendly, zip-neck baselayer top which we've been using extensively during the recent mini ice age...
Merino wool, from merino sheep, is the Rolls Royce of wool - fine fibres mean it doesn't feel scratchy like normal wool, so it's soft and comfortable against the skin. It has natural anti-pong properties making it ideal for multi-day trips and a lifesaver when tent sharing or otherwise living in close proximity and it handles moisture efficiently.
The latter property is worth explaining, as merino is often misunderstood. Unlike synthetics which mostly move moisture outwards and away from the skin, merino tends to absorb more of it and hold it – comfortably – away from the body, though it also evaporates slowly.
That means it's comfortable even as it gets damp and can hold more moisture, in comfort, than comparable weight synthetics. It also means, if you're really sweaty, you can overwhelm it and it does take longer to dry than synthetics. For steadier use though, it's superb.
We used the Sport NTS – Next To Skin – Zip Tee almost constantly through the recent cold snap and it became something of a default choice. The medium-weight merino fabric gives great, soft-feeling comfort and adds instant warmth and the anti-pong properties meant we could use it for several days on the trot without washing it. Sounds vile, but it works and is a massive boon if, for example, you're trekking in an area with limited washing facilities.
Used for low to medium extertion activities like walking, scrambling and climbing, it worked superbly feeling warm, dry and comfortable against the skin. It was less happy with sweaty running when it did eventually become damp and took longer to dry out than we'd expect with a synthetic.
We like the design too. It's neatly tailored and tapered for a snug, athletic fit, flat-lock seams keep it comfy under a pack and the long, 12-inch zipper, gives cooling potential too.
Lovely all-round cold conditions base layer top for anything short of full-on, high-tempo sweatiness. Multi-day use is a real plus as is the lack of stench when you do. It feels well put together too - though bear in mind that we've found merino isn't quite as hard wearing as synthetics in the longer term – it's not cheap, but it's comfortable and effective.