Smartwool specialise in merino wool products and have done a great job with the Classic All-Season Merino base layer. The material is 88% Merino 150 wrapped around a nylon core – the intention being that the nylon core increases durability. I was certainly impressed by the durability of this baselayer.

Price: £79.99 | Weight: (Size small) 165g | Materials: 88% Merino 150 wool, 12% Nylon | Features: Slim fit, Merino 150 fabric with nylon core, plant-based dye. | Sizes: S – XXL | Women‘s version: Yes |

Merino 150 is a thin material and can be damage prone, but I found this garment to be pleasingly resistant to abrasion or damage by over-stretching. The seams are flatlock construction, and the stitching is dense and high quality. I had no issues with the seams causing any chaffing or itching, even when jogging in damp conditions. The fabric feels soft on your skin.

It should be noted that I tested a size Small when I usually wear Medium, and the sizing was just right. The fit is slim and the base layer contours nicely to your body. I found it immediately comfortable, and this remained the case no matter what activity I was doing. This layer has quite a long back-length, and extended below my waist a little further than any of the other base layers I tested. If you have a shorter back then you may find this less suitable.

I found that both breathability and temperature regulation were superb in a variety of different weather conditions with the Classic All-Season Merino. I had no issues with overheating when walking uphill fast in sunshine and 19°c, and my core felt well-insulated on far colder days when wearing an extra layer or two. It was one of the quickest drying garments in this round-up. Odour control felt a little better than any of the other base layers I tested, so if you are prone to sweating heavily then this will be welcome.

I also appreciated that the layer was coloured with a plant-based dye rather than a synthetic one, and that the wool is ZQ certified – both good news for the environment. At £79.99 it is certainly an expensive choice. However, it is a durable and extremely comfortable base layer, suitable for a wide range of conditions and activities.