SEA TO SUMMIT’S Traverse XtII ULTRA-DRYDOWN -11C/12F sleeping bag is one of the best on the market. Featuring its relaxed mummy style design the Traverse XtII offers a plethora of extremely innovative characteristics that add to the overall comfort and quality that mountaineers, hunters and outdoor enthusiasts demand!
Designed for spring, autumn and WINTER adventures the TRAVERSE XtII will compress down to 8.24 liters in the regular sized bag, weighing only 2lb. 12 oz. The warmth to weight ratio is truly exceptional with the XtII. Although this bag first hit the market in 2011 it continues to set the standard for Ultralight DRYDOWN sleeping bags. Believe me, Ultra DRYDOWN is changing the face of the outdoor market.

iReview Gear Lead Field Editor

If you haven’t done the research SEA TO SUMMIT is an Australian company with its North American operation based in Boulder, Colorado. One of the founders is Tim Macartney-Snape, a mountain climber who completed one of the most challenging ascents of Mt. Everest, the highest mountain in the world. In 1984 as a small group of climbers from the world’s flattest continent pulled off a challenging ascent of Mount Everest where they put a new route up the north face in lightweight style with no oxygen or Sherpa support. Six years later, one of the summiteers, Tim Macartney-Snape, decided to return to Everest after he realized neither he nor any other person who had climbed the mountain had truly climbed the entire 8,848 meters, as that would have meant starting from sea level. That is, no one had yet climbed it from “sea to summit”.
In the spring of 1990 Tim had a swim in the tepid waters of India’s Bay of Bengal then set off on foot across the Gangetic plain toward the distant Himalayan foothills. Four months later, after climbing alone from Base Camp and without the assistance of oxygen, he set foot once again on the highest point on earth. Tim’s solo ascent of Mt. Everest was named the “Sea to Summit” expedition.
Back in Australia, Tim joined forces with climbing friend, sewing enthusiast and design guru Roland Tyson to build a business that could make use of their knowledge of the outdoors to create truly ingenious, well-made but affordable outdoor equipment. They named their company Sea to Summit after Tim’s expedition and the business prospered. Today the Sea to Summit brand continues to provide innovative gear and serves a growing band of outdoor enthusiasts all over the world.

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Just the Facts:

Although I use Sea to Summit gear and sleeping bags on a regular basis I still haven’t gotten used to the extra details and features they go to in assuring customer quality. With the TRAVERSE XtII I received a storage bag, wash bag, compression sack, detailed instructions and a Final Report issued by the International Down and Feather Laboratory showing an analysis of the down used in that particular sleeping bag. Please note that I continue to be extremely impressed and appreciative of Sea to Summit’s extensive planning and attention!

• High loft, premium 850-fill goose down offers superb warmth for minimal weight
• Shell fabric is constructed of a 20-denier ripstop fabric treated with a Durable Water Repellent and a non-woven silicone encapsulated fabric
• Innovative shell manages condensation, allowing moisture vapor to pass through down and siliconized barrier outward; shell repels water and protects the loft of the bag
• Lining is a breathable, durable 20-denier polyester fabric with a soft touch
• Full-length side zipper and separate foot zipper allow bag to be converted from traditional sleeping bag to a duvet/down comforter
• Relaxed mummy shape is cut with a large hood, broad shoulders and large chest for comfort and warmth
• Upper side of bag is differentially cut so that the inner layer is smaller than the outer layer; this creates a consistent thickness of insulation and helps prevent cold spots
• Lower side is cut in reverse so that the inner layer is larger than the outer layer; this allows down to loft up, filling spaces around body in warmth
• Oversize draft tube backing zipper keeps the warmth in and the cold out; zipper is backed by stiff, anti-snag tape for smooth operation
• Interior zipper security pocket is great for stowing small essentials, alleviating middle-of-the-night fumbling and preserving battery performance in cold weather
• Oversize collar drapes comfortably over neck and shoulders, sealing out drafts; dual elastic adjusters
• Preventing cold air from seeping in, offset baffle construction allows the goose down to remain fully lofted and keeps it from shifting
• Sea to Summit’s Traverse XtII bag comes with a Ultra-Sil® compression sack, an oversize mesh storage cell and a large cotton sack
• European Norm (EN 13537) is an independent third-party temperature rating, allowing accurate comparisons across brands with other EN-rated bags. The Lower rating for the TRAVERSE XtII is -11°C / 12°F
• YKK #5 reverse zips, allowing for un-zipping of bag from top and bottom for temperature regulation

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As I previously stated, Sea to Summit’s Ultra-Dry Down has changed the conceptual approach to the down gear market. Simply stated, they utilize a technological process to treat down so that it will repel water. There are other vendors who have also initiated this process but there are many other companies who manufacture down products who simply haven’t chosen to take this “giant step forward” and are still waiting to see if the treated down truly works! IT DOES!
Sea to Summit incorporates a repellant polymer treatment that they apply to the down used in their sleeping bags directly at the factory. Research has shown this process not only protects the down from the internal condensation caused naturally from your body but importantly protects the insulating factors of the down from external moisture. One reason many people have stayed away from using down in the past is the fact that they couldn’t get it dry once it became wet. Now, with the polymer treatments, tests show that Ultra-Dry Down absorbs 30% less moisture, retains 60% more loft and dries 60% faster than traditional down, so that is not an issue.
I’ve always been impressed with how well down compresses. The Traverse XtII compresses down into a supplied high quality 15 Liter UltraSil Compression Sack, which will reduce its volume to around 8 Liters. Sea to Summit uses the ASTM standard for measuring compressed volume; I found I could compress the bag to smaller than the quoted 8.24 Liters if required. More importantly, the mature quality down used in Sea to Summit sleeping bags will loft up quickly once removed from the compression sack, and will continue doing so reliably for years to come – remember, Sea to Summit is confident enough in the down quality to provide a rest report from an independent laboratory, the IDFL. Now, that is impressive.



I refer to myself as a “cold sleeper.” However, on several “brutally cold” adventures in the Henrie Mountains of southern Utah this winter the TRAVERSE XtII has performed admirably, keeping me comfortable. I was impressed that the TRAVERSE performed so well at helping me retain my body heat.
I’m accustomed to sleeping in mummy style bags as I have spent countless nights sleeping out on the mountain in “confined quarters.” The shoulder width in the TRAVERSE felt comfortable, encapsulating my body to allow the offset baffles of Ultra Dry Down to insulate me from the cold as the water-repelling shell sealed in heat. The footbox of this bag is designed to actually taper in three directions. I loved this feature in regards to volume. Anatomically speaking the foot box design was perfect for me. I also appreciated the contoured hood that had ample room with drawcords built deeply inside baffles and away from my face.

Traverse XtII Foot Box


It is common for sleeping bags to use a DWR (durable, water repellent) finish on the outer shell to help repel dampness, and Sea to Summit uses a nano-level DWR on the 20D polyester fabric to help to keep external moisture at bay. However, all sleeping bags used in cold conditions are subject to condensation forming on the inside of the shell – warm moisture vapor from the sleeper touches the cold shell material and turns to liquid.
Other manufacturers claim that the shell material they use is ‘breathable’ enough so this does not happen, but the issue is not breathability, it’s just the physics of warm moisture vapor touching a cold surface.
Sea to Summit has a unique solution to this problem: a thin layer of siliconized polyester is installed immediately below the shell. Moisture vapor from the sleeper can pass through this (from the inside moving outwards), but once it condenses on the inner face of the shell, it cannot pass back through the hydrophobic siliconized layer. This is called a ‘3D Nanoshell’, and it prevents both condensation from the sleeper and external moisture from mixing with the down, which preserves its loft.

Now, you might wonder why you would want this now we have ULTRA DRY DOWN? Well, even UltraDry Down will absorb moisture if it is compressed (which happens when you pack your bag away in the morning). A sleeping bag without the 3D Nanoshell will have the moisture spread throughout the down. In the TRAVERSE, all of the moisture is trapped just under the shell where it can dry out if you have a chance to air the bag, or be squeezed through the shell when you compress it.

The bottom line with this feature is that it enables the down stay lofty night after night on multiple-day trips.
With all my sleeping bags I like to use a silk liner to sleep in as I this keeps my bag much cleaner and protects the material from body oils, salt and odor. Sea to Summit also manufactures a superb liner to be used with their bags. For a sleeping pad, my preference has been the Therm-A-Rest Neo Air. I spend most of my time backpacking and hunting on the high desert plateaus of southern Utah where you have a lot of sand and debris to deal with. For that reason alone I really appreciate the XtII zipper guards that are made of exceptionally light yet stiff 210-denier poly cloth as I have never had a snagging issue. I can tell you that after some hard core use my Sea to Summit XtII still appears as if it were new as the tough polyester shell liner fabric has withstood any issues in regards to tears or snags.
XtII Zipper Guards
The Traverse is very capable of providing outstanding service throughout the year although my preference is to use it during the cold winter months when the temperatures dip to below zero temperatures.
For the reader’s convenience I’ve listed for you a comprehensive list of Technical Features and Specifications that sold me on the TRAVERSE XtII sleeping bag as my choice for winter excursions out on the mountain. These specifications demonstrate very well what a great all around bag the XtII is. As you review the Sea to Summit XtII’s specifications you will quickly find that this company doesn’t take any short cuts. Their goal is to ensure that the sleeping bags they produce are as durable and comfortable as any bag you have ever slept in. The design and features do not leave a stone uncovered. Every detail is addressed.

I strongly believe that your choice of a sleeping bag is one of the most important gear decisions that you will make. I’ve slept in bags that didn’t live up to their temperature rating where I darn near froze my backside off. Then, of course, there are those sleeping bags that are just too heavy and cumbersome to backpack. I’ve also had to deal with zipper and hood malfunctions that allowed cold air to filter in around my body that made for some very long, cold nights.
In today’s high tech world, lightweight, compressible sleeping bags have changed the game. I know that personally, I can’t find an excuse for not having several quality sleeping bags in my gear room that are very capable of meeting all of my diverse backpacking needs. This is where Sea to Summit with their new Ultra-Dry Down stepped into my complicated world of separating lightweight, top-notch sleeping bags from the rest of the field. For months now I’ve been researching the insulating qualities of down when it gets wet.
After using Sea to Summit’s Talus TsII Ultra Dry Down sleeping bag for several months last fall I was convinced this was the way to go as I upgraded to the outstanding TRAVERSE XtII for the cold months of winter. Wow, I’ve been extremely happy with my choice.
The water resistant Ultra Dry treatment has lived up to and exceeded my expectations. I ordered the long in the TRAVERSE and although it weighed just a little more at 3 pounds the comfort was well worth a couple more ounces. The bag still compresses down to practically nothing, thus allowing for extra packing space within my backpack but it also retains its loft! The warmth-to-weight ratio has been absolutely outstanding.
Let me stress how nice it has been to find a sleeping bag with 2-way YKK #5 reverse zips that I can access from the top or bottom of the bag. Sea to Summit’s anti-snag system of poly cloth is absolutely outstanding as I haven’t experienced an issue with material getting caught in the zippers. Now, that is very important compared to other sleeping bag zippers that I have used over the years. These full Length YKK #5 reverse zips, allows for un-zipping of bag from top and bottom for temperature regulation.
When choosing the quality of down that I purchase in my sleeping bags I’m particular as not all down comes from the same source! In my research on Sea to Summit I found that the Ultra-Dry Down insulation they use in their TRAVERSE XtII features 850+loft 90% down cluster premium European goose down that is highlighted with their permanent Nano-level water-repellent polymer treatment to repel moisture. This treatment ensures that the down will dry quicker when wet, retain its loft much quicker and help in assuring a longer life of the bag itself. The quality of the down in combination with the water-repellant treatment is so important.
Most mummy style sleeping bags are designed with narrow chest areas that feel too constrictive when sleeping. I was happy to find that the XtII bag has a larger chest area for overall comfort. Add to this the differential cut shell of the inner lining so that the outer shell’s fabric/insulation can expand outward to provide ultimate loft as well as to reduce cold spots and you now have one of the best sleeping bags on the market.

The TRAVERSE XtII Ultra Dry Down bag will cost you around $500 depending on the website you choose to purchase from (lower prices than this are for the older version without UltraDry Down). Don’t let this price scare you away. If you are truly serious about hunting, mountaineering or other outdoor activities then I believe that Sea to Summit’s Traverse XtII should become part of your gear. The extra features inclusive to this sleeping bag are worth the money you spend. With features such as the internal zip chest pocket, a single hand adjustable hood, anti-snag zip, the cushioned internal hood draw-cord and other high-end technical specifications you simply can’t go wrong. I highly recommend the TRAVERSE XtII. If you follow the common sense tips in regards to taking proper care of your sleeping bag it should last you for the rest of your life.
If you have a warranty issue with any of Sea to Summit’s gear the first step should be to contact the shop you purchased it from. Sea to Summit does have an outstanding lifetime warranty and should address any problems you have with the exception of normal wear and tear. I’ve always believed that outstanding companies will back up their products.

What they could do better:
I just can’t find anything wrong with Sea to Summit’s TRAVERSE XtII. It may be a little expensive but it is an incredible lightweight, cold weather sleeping bag that displays outstanding warmth-to-weight ratio, quality and excellent durability. Great product!

SEA TO SUMMIT Traverse XtII Sleeping Bag Review
  • Functionality
  • Value
  • Ergonomics
  • Durability

One Response

  1. Avatar for Nathan Nathan January 11, 2014