JMT Ultralight Vest

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Minimalist 2 season synthetic insulated vest for light layering. At 4.1 ounces for a size medium the hooded JMT packs tremendous warmth and function in a small, all conditions package. 

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The JMT Vest is our lightest insulated shell. Designed for summer layering in the mountains, it's named after the classic John Muir Trail in the Sierra.

Built with Climashield APEX, a lightweight yet remarkably efficient synthetic insulator, the JMT Vest will retain some warmth when damp, and will dry and recover more quickly than down. 


The JMT Vest is trim and devoid of clumsy features. It is best applied as a windproof, warming layer over one or two thin thermal shirts.

Additionally, the JMT can be put to use as extra core insulation while sleeping, thus making a lighter sleep system possible.

This is not an 'Active Insulation' layer. However the JMT would make a great companion piece to this new breed of outerwear, such as the Patagonia Nano Air Light, for comfort at a full range of conditions with very little weight and bulk. 


This is a simple vest, lean on features, with the focus being as much warmth for the weight as possible. In its basic configuration the APEX insulation makes up over 55% of the total weight.

The JMT is available with a full separating front zipper or a half length pullover style zipper. The latter saves 10-15g, but can also prolong the life of the garment while making it easier to handle in strong winds.

We build it with or without an integrated hood. The hood option is fully insulated and offers complete coverage to above the chin - but it is not helmet compatible. In fact, for most users, only a very thin beanie will fit under this trim hood.

The chart below reflects the JMT with a hood. Choosing a collar will save 20-25g depending on size.

We make the JMT Vest without any pockets. The hood casing is a fixed, pre-tensioned shockcord. The JMT Vest does not have an elasticized waist.

Synthetic Fill

APEX by Climashield, a superior continuous filament synthetic insulation, is the choice here.

For the JMT Vest we use 2.2oz/yd - 75g/m Climashield APEX which is light, compact, and applicable for 2, maybe 3 season use. With minimal sewn through stitch lines (virtually none on the shell), and substantial loft in the APEX, the JMT is surprisingly warm as well as very resistant to moisture from sweat and weather.  


The JMT Jacket can be configured with a 10d shell* in a number of different colors. It's an ultralight fabric for folks who want the lightest, but realize that abrasion and tear resistance is minimal.

Also available is a 7d shell** with advanced weatherproofing qualities.

The inside liner is always the breathable 10d. 

*10d. Smooth, comfortable and about the lightest material possible for practical shell use, at 0.67 oz/yd. Very breathable with minimal moisture repellency. Also the standard inside liner. Black, Moroccan Blue, Burnt Orange, Coyote Brown and Royal Purple.

**7d. A special material based on an ultralight, yet relatively durable 7d base fabric with a breathable micro porous coating. The 0.74 oz/yd Robic excels at shedding mist and light rain. A so-called waterproof/breathable fabric, this high tech shell sports a HH (hydrostatic head) of 1000mm, while providing enough vapor transfer for mild activities (good breathability). 


The cut is aimed at providing a short vest with a trim fit, best when used over only one or two lightweight thermal layers. 

The chart and configuration menu below outlines the many options for sizing the JMT Vest. Tall people may wish to go up in zipper and back length.

Also see here.

The picture shows the JMT Vest in half zip configuration with

the shell in Bright Blue waterproof/breathable 7d ripstop.

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JMT Ultralight Vest

JMT Ultralight Vest

Minimalist 2 season synthetic insulated vest for light layering. At 4.1 ounces for a size medium the hooded JMT packs tremendous warmth and function in a small, all conditions package. 

Product Options
Jacket or Pullover
The Pullover Style features a half length front zipper, and weighs 10-15 grams less.
Pullover Style, with half length front zipper
Jacket Style, with full length separating zipper
Torso Length
Adds a number of inches to the back and front length of the selected general size.
Shell Fabric

Please see our Fabric Page for help choosing the right shell material.

Liner Fabric

Integrated Hood and Collar Choices
Choose how to finish out the head opening. An integrated hood eliminates a collar.
Regular Insulated Collar
Insulated & Integrated Hood
Interior Zippered Chest Pocket
With a vertical opening hidden behind the main front zipper, these pockets are protected yet easily accessed.
The pockets adds 16 grams in size large.
Stuff Sack
Our stuff sacks are pretty dope, but current weight saving trends in ultralight circles eschews this once crucial item. So, opt out and save $ while also being very current.
No stuff sack
Yes, please include a stuff sack