Description

A hooded and splayable jacket experiment [#575] where hardworking warmth meets breathable comfort. A proven workwear cut reimagined in the highest performance materials, soft and dry Daydry Merino on the inside, rugged Bombtwill on the exterior, highly breathable Alpha 120 insulation in-between, with double layered Openform Merino cuffs, a two-way Zipscarf compatible front zipper plus two-way side zippers stretching from hem to wrist for the ultimate in ventilation.

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Fabric

Fabric Story

Hardcore yet secretly soft. The magic of the Bombtwill is twisted in the yarns. Hundreds of tiny nylon 6,6 filaments are air-texturized and spun together into each yarn. Each filament is slightly larger than one denier and the air-texturization crimps the yarns giving them a cotton-like spring and lingerie grade softness. But because hundreds of these filaments are twisted into each yarn the result is thick heavy-duty nylon yarn that's overspec'd for everyday wear. More technically the warp yarns use 200 and change filaments while the weft yarns use 300 and change which are also spun around an elastane core, but who is counting? The important thing is the elegant twisting of the soft into the strong.

The weave itself is quite straightforward, a simple 2x1 twill clocking at 360gsm (10.5oz) and treated with a fluorocarbon free (F0/C0) Zelan R3 DWR. The result is a rugged but relatively lightweight fabric that stays clean, dries quickly and has a whole lot of stay-off-the-body structure. In other words it behaves a lot like denim, but is both lighter and more durable.

  • Fiber Content

    • 96%Nylon
    • 4%Elastane
  • Fabric Weight

    360GSM

  • Fabric Origin

    Woven in Sweden

  • Fabric Construction

    Two-way stretch twill

  • Finishing

    Zelan R3 fluorocarbon-free F0 DWR

  • Fabric Water Resistance

    Light

  • Breathability

    Modest

  • Durability

    Extremely High

Fabric Story

Alpha 120 is a modestly heavy insulation characterized by its extreme breathability, an absolute essential when trying to create warmth without overheating. Designed by Polartec for US Special Forces to use in cold wet conditions, it is a knit insulation created by splicing a spacer mesh into two faces. The result is a particular combination of warmth and openness but most importantly it is a non-migrating insulation, which means it can be paired with far more open face and lining fabrics than most traditional insulations.

  • Fiber Content

    Polartec Alpha 120: 100% Polyester

  • Fabric Origin

    Knit in USA

  • Fabric Construction

    Split knit

  • Breathability

    Extremely High

Fabric Story

Nature and technology intertwined in pursuit of lightweight perfection. A 150gsm jersey made with 75% super soft 16.5 micron top-capped merino and 25% Ciclo branded polyester intimately blended together to a luxuriously soft, dry and breathable performance fabric.

The magic starts with the merino of course, because nothing in nature performs as well. We use a 16.5 micron, top-capped Australian RWS certified merino for that extra softness, plus all the hygroscopic thermobuffering and odor resistance wool is so good at. At 150gsm though the fabric is quite light so it needs to be blended with something to strengthen it up, and if you are blending you might as well add some extra performance.

Merino excels at handling water vapor but doesn’t handle liquid water quite as well, something polyester is exceptional at. Poly both absorbs almost zero water (just 0.4% of its weight) and also wicks it across its surface quickly to speed up drying times. When blended with merino it can also create a slightly less bouncy yarn, which in turn allows for the fabric to be knit into a more open structure for better breathability. In particular we use a Ciclo branded polyester that meets Oeko-Tex Ecoports certification. This polyester includes a biodegradable ingredient that stimulates microbe metabolization in environments where materials like wool naturally break down. Or at least that’s what they claim, we take these claims with a big grain of suspicion, but there does seem to be enough there to at least merit testing it out.

  • Fiber Content

    • 75%16.5 Micron Merino
    • 25%Ciclo branded polyester
  • Fabric Weight

    150GSM

  • Fabric Origin

    Knit in Thailand

  • Fabric Construction

    Jersey

  • UPF

    40+

  • Fabric Water Resistance

    None

  • Breathability

    High

  • Durability

    Average

Fit

Size Chart

in Inches | Measured Flat

SizeXSSMLXLXXL
Shoulder20.7521.2521.7522.2522.7523.25
Chest242526272829
Sleeve Length35.53636.53737.538
Front Length27.528.12528.7529.3753030.625
Pedro is 6'1", 160 lbs and wears size M in Charcoal.

Form

  • Made in

    Manhattan

  • Hardware

    • Zipscarf compatible YKK Vislon #8 two-way front zipper​​​​
    • Two YKK #5 two-way side seam zippers
    • One YKK #3 zipper
  • Pockets

    • Two patch hand warmer pockets
    • One zippered internal chest pocket
  • Construction Details

    • Full splay construction, two-way, x-open zippers allow the sides to be opened from the hem to the wrist
    • Openform Merino cuffs and bottom hem
    • Internal paracord hang loop
    • Black Lightning 2" woven label on right pocket
    • Zipscarf compatible
  • Style Number

    O638

Revision History

  • December 2025:
    • Initial release
    • Name: Bombtwill Alphacore Geojak
    • Colors: Postdenim Black, Smoketaupe, Charcoal

Care

  • Washing

    Spot clean

Photography Credits

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