Mountain Equipment Xenith Jacket: maximum warmth, minimum weight

The wind is howling on the summit, you're taking off your skins and your fingers are going stiff. That's exactly when your down jacket needs to keep you warm. The rest of the day it sits in your pack. On ski tours and alpine tours, one thing matters above all: how much warmth per gram you get.

That's where the Xenith Jacket comes in, the new ultralight down jacket from Mountain Equipment for autumn/winter 2026/27. The British brand takes a different approach to lightweight construction. The baffles are hexagonal.

A down jacket keeps you warm because the down traps air. To make sure it does so evenly, the down is stitched into baffles. The usual solution is horizontal channels. Their drawback: at every seam, the outer and inner fabric lie directly on top of each other. There's hardly any down there, and that's where heat escapes. This is called a cold spot.

On the Xenith, Mountain Equipment replaces the channels with hexagons. According to the manufacturer, the idea came from a study published in 2023. Its finding: hexagonal baffles could be more thermally efficient than straight ones. The shape is familiar from nature, from snowflakes, tortoise shells and basalt columns. According to the manufacturer, the fill weight and down density are optimally matched to the new baffle shape.

Mountain Equipment expects four benefits from this. The down lofts evenly across the whole jacket, so the loft, meaning its ability to puff up, is the same everywhere. In the small, closed cells it can't shift and always keeps you warm where it should. There are fewer cold spots at the seams. And if the insulation gets damp, it dries faster because the down has a water-repellent treatment.

In the climate chamber and in the field, the manufacturer says the Xenith showed "significant progress" compared with down jackets with narrow baffles and a similar weight.

The Xenith is filled with goose down: 120 g in the men's jacket and 100 g in the women's. The down has a water-repellent treatment and a fill power of at least 800. According to the manufacturer, it is certified to the Responsible Down Standard (RDS) and DOWN CODEX®.

The outer and inner fabric is called HELIUM 10D. The number refers to the yarn thickness in denier, and 10D is very fine. The fabric is windproof and packs down small. According to the manufacturer, the water-repellent finish is PFAS-free.

The hood is insulated and fits over a helmet. The jacket packs into its own stuff sack, which is also hexagonal. Mountain Equipment designed the Xenith for alpine tours, ski mountaineering and multi-day treks: for freezing early starts, fast summit pushes and long distances.

The Xenith is available as a men's model and a women's model. The women's version weighs 280 g (size 12).

The Xenith isn't enough for everyone for a whole winter in the mountains. If you stand around for long periods in sub-zero temperatures or head out on an expedition, you need more down, and that adds weight.

The Jokla is the next step up: 200 g of goose down in two layers of baffles whose seams don't line up. At 540 g, it weighs a good one and a half times as much as the Xenith. In return, you have more in reserve on long, cold days.

The Lightline is the classic in the range, filled with duck down. At 40 denier, its outer fabric has four times the yarn thickness of the Xenith. A good choice if you also wear the jacket at the hut and in everyday life.

The K7 is the warmest of the four: 300 g of goose down in box-wall baffles, where fabric walls keep the down at full height even at the seams. Made for high mountains and long periods standing still. For a normal ski tour, it's more jacket than you need.

The Xenith is built for tours where you want to travel as light as possible and still have a real warmth boost with you.