The North Face Summit L4 Jacket

Sam Shaheen reviews the North Face Summit Series L4 jacket for Blister Review
The North Face Summit Series L4 Jacket

The North Face Summit Series L4 Jacket

Size Tested: M

Stated Weight: 500 g

Front Zipper Length (size M): 67 cm

Stated Features:

  • Articulated patterning designed specifically for alpine comfort and mobility
  • Lightweight yet durable nylon mini-ripstop
  • ThermoBall™ powered by PrimaLoft® synthetic insulation for warmth and all-weather versatility; bottleneck quilt construction minimizes stitch-through and stabilizes insulation for more warmth and durability
  • Unibody construction minimizes cold spots and enhances overall garment strength
  • Brimless, insulated hood with high front collar fits under a helmet and provides maximum warmth with minimal bulk
  • Vislon front zipper with offset draft flap for added weather protection
  • Minimalist chest and hand pocket zippers for less bulk when layering
  • Clean-finish cuffs for minimal bulk
  • Internal, secure-zip security and stash pockets
  • Hidden hem-cinch adjustment

MSRP: $300 USD

Reviewer: 5’10”, 135 lbs

Test Locations: Aspen and Denver CO; Vaud, Berner Oberland and Valais Switzerland
Days worn: 15


The L4 jacket is part of The North Face’s new Summit Series, which is TNF’s limited run of alpine-oriented, high-performance pieces that showcase new technologies and manufacturing techniques.

I have been very impressed with TNF’s new line so far (specifically, with the L4 Jacket and the L5 pant), and I’m very interested in the future of the Summit Series.

The L4 is a synthetic insulation piece, situated between a warmer belay jacket and a standard Patagonia Nano Puff / TNF Thermoball mid layer on the warmth scale. The L4 doesn’t actually have many direct competitors, since almost all of the jackets of a similar warmth are made with down insulated. But the L4 is quickly becoming my go-to insulator for just about any activity. My down pieces are almost always staying at home these days, and the L4 Jacket has reminded me that synthetic insulation has a few advantages beyond just keeping its loft while wet.

Sam Shaheen reviews the North Face Summit Series L4 jacket for Blister Review
Sam Shaheen in The North Face Summit L4 jacket.

The fact that synthetic insulation is heavier with respect to its loft volume means that it has a bit of thermal mass. Where fancy down jackets are all air and super puffy, the L4 is low profile and a bit more dense, offering packable warmth without the huge puffiness and “airy” feeling of down insulation. And it does all of this while being much warmer than an analogous 800-fill down with the same loft, at only a small weight penalty. (More on this a bit later.)


The L4 is a sewn-through synthetic insulator. The insulation is The North Face’s proprietary PrimaLoft, which is a Thermoball down analogue. Coming in at a stated 500 grams, this piece is definitely heavier than “standard” weight synthetic mid layers like the Patagonia Nano Puff (357 g) and TNF Thermoball (375 g). But that additional weight of the L4 gets you two things: (1) lots of pockets, and (2) more insulation.

The quilting on the L4 is something I have come to call a “digital onion stitch.” Reminiscent of the onion quilting of the good ol’ days, this updated onion stitch is by far my favorite stitch pattern on an insulated piece that I have used. It has a great look—it is unique without being goofy. It’s a nod to the old school with a distinctly updated feel. The way the stitch falls on the jacket means that there are no awkward creases or folds that can develop with other stitches (I’m looking at you, Thermoball). And it aesthetically separates itself from the horizontal baffles of the down world.

Functionally speaking, the stitch does a great job of distributing insulation while keeping the amount of quilting necessary to a minimum (which helps save on weight and durability).

In short, this digital onion quilt gets two thumbs up from me. Well done, North Face.

Similar to the Thermoball, there are nylon panels in the front of the jacket to eliminate wind penetration from the front (for reference, the Patagonia Nano Puff has a full nylon liner, and is 100% windproof). The panels do a good job of making the L4 effectively windproof, and I have never felt wind coming through this jacket.


The L4 has a great fit. Because the Nano Puff and Thermoball are marketed to a very broad audience, they have a very generic cut: they are boxy, and generous in the body and sleeves. That fit is designed to fit ‘okay’ on as many people as possible, while fitting great on almost no one.

The L4, however, is aimed at a narrower audience. It is fit very athletically and anatomically. The arms have a perfect taper, and are articulated for excellent comfort. The body is wider at the shoulders than the hips, so it fits nicely around an athletic form without having too much dead space.

The only downside to this athletic fit is that the sleeves are a touch too narrow to comfortably throw it over some of my shells. The Patagonia Knifeblade fits okay under the L4, but the Mountain Equipment Tupilak gets quite crowded in the sleeves with the L4 over it. So I find myself taking my shell off and replacing it with the L4 at the summit.

For synthetic insulators, the L4 has the best overall fit I’ve used. It hugs the body and I never think about it when it’s on, which is definitely high praise.

There is only one part of the fit that doesn’t jive well with me: the cuffs. The cuff is cut long, so it hits me just past my knuckles when my arms are at my sides. There is an elastic piece inside the sleeve that ends up right around my wrist, but the cuff extends well past this piece to cover most of my hand. There are times when this is actually quite nice (if I am not wearing gloves, it keeps my hands plenty warm) but on the whole, I would prefer a traditionally cut cuff. It is just too long on this piece.

Pockets & Features

The L4 is a fully-featured insulator. It has three exterior zip pockets (two hand warmer, one napoleon), two interior pockets (one zip and one drop in), a close fitting hood and a drawstring hem adjustment.

This three-exterior-pocket setup is common and standard for a reason: it works well. I appreciate the inclusion of a drop-in pocket on the inside. I use that pocket often, but the interior zip doesn’t get much use from me.

The drawstring hem adjustment is pretty standard: the adjustment cords are hidden in the hand warmer pockets. The elastic cord is about 3” too long, but that’s not a big deal.

The Hood, Warmth, Etc.

Leave a Comment