Introductory Price!

Forty Below® ZVB Vest™

Temporarily available at a special introductory price. Be part of our Beta/Demo group,get a reduced price, and help get us feedback on performance and features! (Limited time offering.)

The new updated Forty Below® ZVB Vest™  is a “zone vapor barrier” vest designed specifically for helping eliminate moisture build up in your clothing layers between you and your backpack! No more soaking wet back in your jackets or pack!

Please see below for additional information and specifications.

Size and Colors *


Forty Below® ZVB Vest™: now available as a NEW lighter weight version

Regular Price $105.00

Be part of our Beta/Demo group, get a reduced price, and help provide feedback on performance and features! (Limited time offering.)

A truly revolutionary clothing piece! The Forty Below® ZVB Vest™ is great for folks who sweat a lot and are trying to reduce moisture buildup in the insulating layers between your back and the backpack. Designed as a “zone vapor barrier” to keep perspiration moisture from accumulating in the layers of clothing between you and your pack.

We invented this unique vest back in the 1980’s to help keep down climbing suits, down jackets, fleece, and wool mid-layers from getting wet in the back from perspiration from sweating, between you and your backpack, while climbing in extreme cold and high altitude zones. Once a down jacket gets wet it losses a significant amount of insulation and is very difficult to get dry, especially on long trips and expeditions. This solves the problem that some folks have with excessive sweating, and are looking for tools to manage that moisture and help keep insulation values in those layers.

This new version of the 40 Below Zone Vapor Barrier vest now embodies the state of the art with new special lightweight materials and a dynamic fit for maximum performance and comfort. These new elements now makes this vest capable of being used for not only high altitude and extreme cold climbing, but also performance athletes participating in cold weather events such as fat tire mountain bike races, cross country and snowshoeing races, and long distance endurance races, such as the ITI Iditarod, Arrowhead 135 Ultra, Fatpursuit, and many others around the world. Very practical also for folks who just normally sweat a lot, for hiking, hunting, and even outdoor working in the cold. In addition, another common use in more temperate conditions to reduce/eliminate moisture buildup on your backpack back panel fabric and shoulder straps!

Ever take your pack off to find an excess amount of water in your back insulation, only to quickly turn to ice? This vest will help eliminate most of this problem!

The Forty Below® ZVB Vest™ which is a vapor barrier vest clothing piece, is designed for activities in a wide range of cold weather conditions, and very specifically helpful in extreme cold conditions. When you are done with your activity, you can take off the vest and have your outer jacket or insulation layers that are not soaked in the back area! Your base layer will be damp as it normally is, but that is usually much easier to air dry than an insulating layer for sure!

  • The front closure are 4 small snaps, to keep the vest light and not interfere with other clothing layers.
  • Longer cut in the back to help insulate kidney area.
  • Shorter cut in the front to help stay out of the way of backpack hip belts, climbing harness, etc.
  • No Pockets: This helps reduce weight, reduce front bulk, plus enable as much sweat moisture vapor in the front of the vest to pass through. 
  • Superlight weight!!  ONLY 5 ounces for size “M/L” (medium-large)!
  • Packed size: Smaller than a 12 oz beer can! (“M/L” (medium-large size) measures only 3.75″ x 2.25″ x 2.25″ !
  • Colors: FRONT: WHITE, Brown.  The White front with our unique Snow and Ice “40 Below ZVB” graphics in Blue, and BROWN front with our unique Snow and Ice “40 Below ZVB” graphics in slightly darker brown, almost not visible    BACK: Black
Sizes:  “ZONE RANGE” SIZING: 6 sizes, each of the sizes is designed to fit a “range”, and the vest is made of stretchy materials to flex and allow for a better fit in motion and when wearing a pack.

  • X-Small/Small (Fits folks who are usually size X-Small to Small in a base layer) Chest Circumference: 39 inches/99 cm and stretchy.
  • Small/Medium (Fits folks who are usually size Small to Medium size in a base layer) Chest Circumference: 41 inches/104cm and stretchy.
  • Medium/Large Fits folks who are usually size Medium to Large size in a base layer. Chest Circumference: 43 inches/109cm and stretchy.
  • Large/X-Large Fits folks who are usually size Large to X-Large size in a base layer. Chest Circumference: 45 inches/114cm and stretchy.
  • X-Large/XX-Large Fits folks who are usually size X-Large to XX-Large size in a base layer. Chest Circumference: 48 inches/122cm and stretchy
  • XX-Large/XXX-Large Fits folks who are usually size XXL to XXL in a base layer. Chest Circumference: 54 inches/137cm and stretchy.
The “front panel zone” is made of a stretchy thin polyester fabric that allows moisture to wick well and dry fast. The front shape is shorter than the back to help keep out of the way of hip belts and climbing harnesses. The large arm openings allow for maximum freedom of motion and reduced restriction. Front closure is 4 small snaps to help keep it lightweight, low profile, and maximum moisture passage.
The “back panel zone” of the vest is made of a specially made stretchy coated lightweight polyester fabric that does not allow moisture to pass through it. It flexes with your body movement, which is perfect for comfort when wearing a backpack! The back shape is longer cut to fit under hip belts better and slightly insulate the lower back and kidneys.

See it in Action

New video and comprehensive review from Alan of “Dirty Teeth MTB“:

“Anyone who has carried a pack and sweated and soaked their insulation, which then froze or didn’t dry should realize what an advantage this radical product could be in your climbing wardrobe. I give it a 9 on a scale of 1 to 10…”

Marc Twight Rock and Ice Magazine Product Review, February 1993

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