David Lintern tests the Arc’teryx Atom SL

The Arc’teryx Atom SL has previously featured in our guide to the best fleeces. The key player here is the brand’s own insulation called Coreloft, a non-woven siliconised polyester in sheet form, that traps heat and does not retain water. The Arc’teryx Atom SL also has a weather resistant outer face that shrugs off wind and showers.

Weight: 270g | Outer: Tyono 20, DWR finish | Sizes: Various | Insulation: Coreloft | Women’s version: Yes

The hood does not contain any Coreloft and is therefore low profile and can be tucked inside the jacket if not in use. It does have a slightly stiffened visor and a volume adjuster. The inner sleeves and torso panels are made of a thin fleece to improve breathability and fit. There are two handwarmer style pockets but no chest pocket, which I’d prefer to see on a jacket like this. The fit is slim but there’s enough room under my medium for a baselayer, and very thin mid.

The fleece parts are Bluesign approved, and the dope dye process used has been designed to reduce Co2 emissions and save water.

The resultant jacket is a practical, no fuss and versatile piece that combines the properties of a mid-weight fleece and a windshirt. It’s useful for active, shoulder season use in the mountains, or winter layering with a hardshell, but it works especially well across running, cycling and mountaineering where simplicity wins out over the ability to fine tune temperature. It packs down small, continues to re-loft over time and is resistant to weather.