'Masses of down and serious build quality means the Summit Series L6 Jacket is uncompromisingly heavy, but also insanely warm - you'll need to be going somewhere seriously cold to justify owning one. Think of it as a sleeping bag disguised as a jacket and you won't be far wrong...'

Outdoors Magic: Insanely warm, high-tec welded z-baffled construction, huge helmet hood, plenty of pockets, feels seriously tough, surprisingly unrestrictive. And did we mention how ridiculously warm it is?

Outdoors Tragic: As heavy as some expedition sleeping bags. The integrated thumb-loop cuff design won't suit everyone by limiting glove choice. Expensive.

Outdoors Grabbit? For most use the L6 is overkill in the same way as machine-gunning a rabbit would be. It's improbably warm and improbably weighty, but if you're off somewhere seriously cold - the Himalaya in winter or the Andes or maybe the polar regions - and need a mega-warm belay jacket built to seriously high standards, you won't go far wrong with the L6. You won't want to be carrying it around too much though and finally, the integrated thumb-loop cuff design won't suit everybody, though you could always cut it out if you prefer.

L6 Jacket Ratings

Outright Warmth [rating score="5"]

Packability [rating score="2"]

Damp-proofing [rating score="3.5"]

Overall: [rating score="4.5"]

Full Specification

Ultra-cold condition jacket / 800 fill power RDS goose down / FuseForm outer shell technology gives zoned toughness / articulated fabric for mobility / deep neck drop / welded Z-baffle construction / helmet-compatible insulated hood / YKK Vislon main zip with off-set draft flap / twin chest and hand pockets with water-resistant, urethane-coated zips / external chest pocket allows internal access to stashed gear in stretch mesh stash pockets / hidden adjustable cinch cord with

adjuster in hand-pockets

Full Review Below

The North Face Summit Series L6 Down Jacket  sitting on a gritstone outcrop
The North Face Summit Series L6 Down Jacket  hood
The North Face Summit Series L6 Down Jacket  hood with helmet

The North Face Summit Series L6 - Fill

Cards on the table, originally we were going to review the Summit Series L3, the L6's micro-baffled little brother as part of our 2017 Insulation Group Test, but life and postal issues got in the way and we ended up with an expected audience with the L6 instead.

It's part of TNF's elite level Summit Series capsule collection aimed at serious level technical mountaineering and designed to be an ultra-cold conditions belay and all-round warm jacket. The insulation is top-notch 800 fill power goose down for optimum warmth to weight ratio.

Responsible Down

It's certified to the Responsible Down Standard (RDS) by Control Union, so it's traceable and produced according to ethical standards. Ethical down sourcing is a complex process and there are several rival standards out there including Mountain Equipment's Down Codex and Patagonia's Traceable Down.

There is some debate over which is the most ethical standard, but Four Paws, rates TNF's down as being close to the top of the pile with only Patagonia and Fjällräven scoring higher.

The North Face Summit Series L6 Down Jacket  thumb-loop cuff detail
The North Face Summit Series L6 Down Jacket  chest pocket

The North Face Summit Series L6 - Performance

There's no getting away from the fact that at a measured 1140g for a medium, the L6 is seriously weighty for a jacket, but the two things you need to know are that it's insanely warm. And very thoroughly engineered.

Cards on the table: so far the L6 has brushed off the coldest conditions the UK winter has to offer without batting a down-filled eyelid. Using it in British conditions is like taking a Formula One car to a go-kart track.

Nope, even though it's not temperature rated, the jacket is intended for seriously sub-zero climes. High altitude peaks in the Himalaya. The Alps in deep winter. The high Andes. Alaska. And the polar regions, are its natural habitat.

Anywhere that you might want to wear something that essentially feels like a sleeping bag disguised as a down jacket. Not that pure infernal warmth is all the L6 has in its locker, far from it.

It's seriously put together using the best technology a massive corporation like The North Face can sources. The Z-baffled construction uses welded seams to eliminate stitching and minimise cold-spots for example.

And the tough-feeling micro-gridded outer fabric also utilises TNF's FuseForm technology to increase abrasion resistance in important areas. The darker green panels aren't separate, they're part of the same piece of fabric as the lighter ones, they're woven differently for added toughness. Clever huh?

That's one serious hood. Snug it up and cinch it down and you're talking full facial protection - image: Jon

The hood is a serous piece of insulation too. First the collar is very high, so even when the main hood isn't deployed, you get a high level of neck and chin protection. The actual hood is heavily insulated and sized to fit easily over a climbing helmet, while still allowing a bunch of facial protection. Ideal for expedition belay jacket use.

It works without a helmet too. Loads of coverage for your face with just a slot to see through. It's like being enveloped in warmth.

And then there's the detailing. There are loads of neat touches: remote hem adjusters with the pull-cord housed in the hand-warmer pockets. Chest pockets with a secondary internal zip which, in turn, means you can access the contents of two internal stretch mesh stash pockets without undoing the main-zip and wasting previous heat.

Easy-grip zip-pulls which work fine with gloves, because you will be wearing gloves with this jacket. And even an emergency fluoro orange pennant with reflective logo which sits in the lefthand chest-pocket just in case you need to be spotted more easily.

If there's one thing we'd maybe query, it's the integrated Lycra thumb-loop cuff construction. It works fine with lighter gloves and shorter-cuffed  ones like, say, the MHW Hydra Pro, but we found it struggled a little with gauntlet-style gloves. To be fair, the obvious solution, would simply be to remove the inner, thumb-looped cuff if it doesn't work for you.

Cinch cord for the hem is hidden away inside the insulated hand-warmer pockets - image: Harsharn Gill

The North Face Summit Series L6 - Verdict

This is one serious cold conditions jacket. So serious in fact, that in all honesty, most buyers are unlikely to get anywhere near its capabilities. It's like wearing an expedition sleeping bag, but with a lot more mobility. Add in some impressive technology and it's a thing to wonder at.

The pay-off for all that insulation and tech is a hefty 1140 gramme measured weight and a £550 price-tag. For most of us, sitting on belay or bivvying out at -30˚C or less is a pipe dream, but if that sort of thing is your bag, then this might just be your jacket.

For the UK though, it's way OTT. And ridiculously warm. Did we mention that?

More Information

See www.thenorthface.co.uk

Also: Best Down and Synthetic Insulated Jackets Tested 2017