Welcome! Ultralight backpacking is my passion, and keeping up on new technologies, gear, and techniques relevant to UL backpacking is what floats my boat. I'm always looking for the lightest, most functional gear to improve a lightweight or ultralight backpacking kit, and report my impressions and field testing results here. For hikers wanting to keep up on the latest and greatest ultralight backpacking gear, this is a good place to hang out. Also, there is a lot of information here (and on our informational website Southwest Ultralight Backpacking) on useful techniques and backcountry etiquette -- food for thought for hikers wanting to lighten their load and their impacts.

My goal for Ultralight Insights is to understand, test, and report on new technologies and gear of interest to lightweight and ultralight backpackers. It's a passion after all, so we just plain enjoy talking about it. I hope readers will add their own wisdom and comments, respond to my questions, ask their own questions, and correct me if I get something wrong. Happy hiking! Will

Wednesday, September 26, 2018

GEAR REVIEW: Zpacks Classic Sleeping Bag and Goose Down Hood

The Zpacks Classic Sleeping Bag delivers on all fronts; they have a size to fit most everyone, its lighter weight for its temperature rating compared to other manufacturers’ bags, its highly versatile to use, and it’s a great value.

By Will Rietveld

Over about 18 years as an outdoor writer and gear tester, I have reviewed a lot of sleeping bags, and find that an ultralight sleeping bag is one of the more difficult gear selections. The challenge is to get enough warmth and inside room, while minimizing weight.

I have certainly found out what doesn’t work: many ultralight bags are way overrated, so they are not warm enough; many bags are too darn tight, so there’s no room to wear insulated clothing inside, and warmer versions are too heavy.

I finally found the Zpacks Classic Sleeping Bag, which has been around for awhile, but it took me awhile to appreciate it. This review is basically a testimonial of my evolutionary experience with ultralight sleeping bags, and how I arrived at, and love, the Zpacks Classic Sleeping Bag.

The hoodless Zpacks Classic Sleeping Bag has the zipper on the bottom side. Its available in 24 different combinations of temperature rating, length, and girth. (Zpacks photo)

Specifications and Features

Zpacks www.zpacks.com
Classic Sleeping Bag
Shell and lining are 0.59 oz/sq yd Ventum ripstop nylon with DWR, insulation is 900 fill-power white European Goose down, ¾ length YKK #3 double-pull one-way zipper
Temperature/Girth/Length Options
3 temperature options (35F, 20F, 5F) x 3 girth options (slim, standard, broad) x 4 length options (short, medium, long, X-long). The broad girth is available only in long and extra long lengths.
5F, Standard width, Long length tested. Mfr. specified weight 24.8 oz, measured weight 24.3 oz.
Smaller vertical baffles on upper part of bag prevents  down from shifting to sides, 30% overfill in chambers to allow for down compression over time, horizontal baffles in footbox area, black lining for quicker drying, zipper on the bottomside of the bag, flat clip at top of zipper keeps zipper from opening, elastic cord closure around the neck. No zipper baffle or neck baffle, hoodless.
Goose Down Hood
850 fill-power down, same shell fabric, 1.3 ounces (1.55 measured), $65


The Zpacks Classic Sleeping Bag is unconventional compared to a traditional mummy bag. It’s a minimalist bag that substitutes versatility and functionality for weighty features.

The bag does not have a hood. A ¾-length zipper is located on the bottom of the bag, so it doesn’t need a zipper baffle. There is no neck baffle inside the bag; rather a thin drawcord draws the top of the bag snug around your neck.

The bag is designed to be used as a quilt on warmer nights (above) or as a sleeping bag (previous photo) on colder nights. (Zpacks photo)

A light hat is needed on warmer nights, and warmer headwear like the Zpacks Goose Down Hood is needed on colder nights.

By the numbers, the Classic Sleeping Bag has a lot of warmth for its weight. It’s 0.59 ounce per square yard Ventum ripstop  nylon shell and lining is the lightest woven fabric I have encountered to date. For the size tested, the shell, zipper, and drawcord account for only 26% of bag weight, the remaining 18.2 ounces (74%) is 900 fill-power down.

While other sleeping bag manufacturers limit the number of temperature and size options, Zpacks does the exact opposite. The Classic Sleeping Bag is available in a total of 24 temperature, girth, and length options. That’s amazing!

To get in/out of the bag, one can turn the zipper to one side to open/close it, then shift the zipper to the bottom; or simply enter the bag from the top. 

The head end of the bag has a thin elastic drawcord to snug it around your neck. A flat clip at the top of the zipper keeps it from opening on its own. (Zpacks photo)

Ventilation options (from warm to cool air temperatures) are: open the bag and use it as a blanket; sleep with the partially open zipper on top, drawcord open; sleep with the zipper closed on top, drawcord open; and sleep with the zipper on the bottom and drawcord drawn up around the neck. Headwear would range from none to the Zpacks Goose Down Hood.

The Zpacks Down Hood (made by Goosefeet) is insulated with 850 fill-power down and uses the same shell fabric as the Zpacks Classic Sleeping Bag. It's anatomically designed to cover the head and has a dropped tail on the front and rear to tuck into a jacket. A thin drawcord on the front draws it up around the face; it will cover your eyes while sleeping if you want. Weight is 1.3 ounces and MSRP is $65.

Sleeping Bag Conundrums

There are lots of ways to go wrong when choosing an ultralight sleeping bag, and most manufacturers don’t help much in providing more choices or selection assistance.

Typical ultralight sleeping bags from mainstream manufacturers tend to be overrated for warmth (despite the EN standard), they’re available in only a few sizes (typically Regular and Long), are too tight in shoulder girth (often 58-59 inches), and expensive.

Ultralight backpackers tend to choose a lighter bag and wear camp clothing inside to extend its warmth. Then the issue becomes finding a bag with enough shoulder girth to accommodate that. There are few bags available in Regular length that have enough shoulder girth, I prefer 61 inches or more, but many bags are only 58 or 59 inches. I’m fairly thin and I find it very difficult to zip into a bag with 59 inches of shoulder girth. So I often resort to getting a size Long to get the girth I need, but I get unneeded length along with it.

It’s not a bad idea to opt for a warmer bag to avoid getting cold, and to compensate for manufacturers’ optimistic temperature ratings. A bag rated at 20F with at least 61 inches of shoulder girth is a good choice for many backpackers, however body size and individual thermal needs vary a lot.

Additionally, there are individual preferences for a full-length zipper (or not), attached hood (or not), or the simplicity and freedom of a quilt.

Through trial and error, my personal preference is for a quilt when temperatures are warmer (above 35F), and a mummy bag when it’s colder. A mummy bag is simply more thermally efficient – it holds heat inside better. However, it’s hard to find a mummy bag that’s warm enough, roomy enough, and light weight (all 3). That’s the conundrum.

Then I discovered, through friends that have them, the Zpacks Classic Sleeping Bag. The beauty is you get to choose your desired temperature rating, shoulder girth, and length – and Zpacks provides simple guidance on how to choose. Additionally the bags are very light weight and reasonably priced.

A 20F rated bag would normally be sufficient for me, if I wear camp clothing inside the bag on colder nights. However, I chose the 5F bag for three reasons: (1) I’m getting older and don’t have much body fat, so I get cold easier; (2) the 5F Standard girth/Long length bag weighs just 24.8 ounces, which is about the same as a 20F bag from other manufacturers; and (3) I wanted a warm bag to extend my backpacking into the shoulder seasons. Zpacks specifies that this bag has 18.2 ounces of down fill, which is good assurance that the bag will be warm.

This all sounds good; so how did it work out? Read on for my testing report and evaluation.

Field Testing

I tested the Zpacks Classic Sleeping bag on 5 backpacking trips and one road trip in late summer and fall in Central and Southwestern Colorado. I usually camp on the alpine tundra above 12,000 feet, where it often drops down to freezing at night. This photo was taken in late September, when the tundra is colorful and nighttime temperatures are dropping into the low 20s. The shelter is the Zpacks Duplex Tarp.

I followed Zpack’s online advice to choose my bag size. I’m 6 feet tall, so I went with size Long. To determine bag girth needed, Zpacks recommends measuring the girth around my chest and arms (46 inches), adding 8 inches for wiggle room, and adding a little more if I want extra wiggle room. So, 46 inches plus 8 inches plus an extra 5 inches adds up to 61 inches, which is their Standard girth bag and my desired girth.

The Zpacks sizing guide worked well for me; the bag I tested is a good match in length and girth. I’m 6 feet tall and the size Long bag is a good fit for length. The 61-inch shoulder girth allows sufficient room to wear a lightweight down jacket inside the bag if needed. So far I have only needed to wear a baselayer plus an ultralight down jacket. From my previous years of mummy bag testing, I have found that I need at least 61 inches of shoulder girth, so the Zpacks sizing guide is spot on.

During my testing I typically camp in the alpine zone at elevations of 12,000 or more, so summertime nighttime lows can drop to freezing. By late summer and early fall I had encountered low temperatures down to freezing (3 nights) and below freezing (27F, 24F, and 14F) three nights.

I comfortably used the bag as a quilt in nighttime temperatures down to about 35F, and really like the quilt option when temperatures permit. At about that temperature (which I call the 4 o’clock freeze) I start feeling cold spots where the quilt is not adequately tucked in. Then I zip up the bag and switch to sleeping bag mode. On the coldest nights I donned the Zpacks Down Hood and tightened the drawcord to snug the bag around my neck, and slept warm as toast the rest of the night.

On my coldest night, in late September camped on the alpine tundra at 12, 500 feet, I wore several layers of camp clothing inside the bag and stayed comfortably warm. The bag has sufficient girth to accommodate the extra bulk. My water flask and rehydrating breakfast were frozen solid.

I personally like a hoodless sleeping bag. With the accessory down hood the system is equivalent to a mummy bag. The advantage is I turn over inside the Zpacks bag, rather than turning a conventional mummy bag with me so the hood is in the right direction.

I also have no issues with entering a sleeping bag from the top; it’s simply not that difficult to slide in. If that is not an option for you, it is easy to shift the zipper to one side or the other and enter/exit using the zipper. It doesn’t have a zipper baffle, so snagging is not an issue.

As with any down sleeping bag, it’s a good idea to hold the bag up against the sky to check the down distribution. The down will shift to some degree in most bags, so it’s important to check for areas where the down is sparse, and shake the bag accordingly to more evenly distribute the down. So far, the Zpacks bag has performed well in this regard.

Warmth-wise, the 5F-rated Zpacks Classic Sleeping Bag has been reliably warm so far, which is really nice; no more chilly nights in a 30F bag. I expect it to be warm into the single digits if I wear down booties, lightweight down pants, and a down jacket inside, along with the Zpacks Down Hood. Those are items I normally take for campwear for shoulder season camping at high elevations.

 This photo shows how much the bag lofts up. For comparison, the sleeping pad is 2.5 inches thick. I measured the double layer loft at 8 inches, which is a lot. According to the Backpacking Light table of sleeping bag loft versus temperature rating, this comes out to a -20F rating (!)


Some hikers may see the Zpacks Classic Sleeping Bag as unconventional, and it is, but it is one that should receive serious consideration by anyone looking for an ultralight sleeping bag. With 24 temperature, length, and girth options, there should be a good fit for most any body. Ultralight bags from many other manufacturers are simply too tight, with shoulder girths of only 58-59 inches. Also, a good way for a short person to save weight is to get a size Short bag, and Zpacks has one that will fit your dimensions.

The bag is also the most versatile I have tested. It can be used as a quilt in warmer temperatures, with the zipper partially open or on the topside in chilly temperatures, and as a mummy bag equivalent (using a down hood) when it’s cold.

The Zpacks bag also provides the most warmth-for-the-weight I have encountered. The shell, zipper, and drawcord weigh only 6.6 ounces for the bag I tested, the remaining 18.2 ounces is 900 fill-power down. I was able to get a 5F rated bag for the same weight as most manufacturers’ 20F rated bag, and some 30F rated bags.

Finally, the Zpacks Classic Sleeping Bag is an excellent value. Most manufacturers’ 20F and 30F ultralight bags are priced in the $400 to $500 range; the 5F bag tested is $399, and a 20F version is $379.

Overall, the Zpacks Classic Sleeping Bag delivers on all fronts; they have a size to fit most everyone, its lighter weight for its temperature rating compared to other manufacturer’s bags, its highly versatile to use, and it’s a great value.

Likewise the Zpacks Down Hood is the lightest to be found at 1.3 ounces, and it is well fitted and very warm. 


  1. There is no substitute for trying a bag, preferably in your own backyard. I tried the Zpacks 20F, wide/long at 40F. Too hot, even with my feet out and in quilt mode. I exchanged it for a 30F, Xwide/long. Love this bag, down to about 30F with a down sweater inside.

  2. Great review, I also like a bit of room in my bag. How do you find the footbox? Is it snug or can you wriggle your toes ok?