Gear Review: Therm-a-Rest Space Cowboy Sleeping Bag 45-Degree

Therm-a-Rest Space Cowboy 45-Degree Sleeping Bag

Basic specs

  • Brand: Therm-a-Rest
  • Product Name: Space Cowboy 45-degree Sleeping Bag
  • Weight: 19oz (regular length)
  • Packed size: 7in x 10in
  • MSRP: $139.95

Circumstances of Review

Thermarest Space Cowboy

Ready for a cozy night on the Colorado Trail!

I was really excited when I first read the specs on this bag. I’ve been in the market for a lightweight summer bag to use during the wet, hot, humid southern Appalachian summers. Coming in at just over a pound with a 45-degree temperature rating, the Therm-a-Rest Space Cowboy seemed to fit the bill. I wanted to test this bag in a couple of different climates. First, I spent five days camping on the Appalachian Trail in southern Virginia in May. I was expecting rainy season in Virginia, and I wasn’t disappointed: it rained every single day. Since this bag is touted as being water-resistant, I wanted to see if it lived up to expectations. Hint: it did. 

The second place I tested this bag was intended to really push the bag to the limits of its temperature rating. I spent two weeks camping and backpacking in Colorado in early July. While Colorado is significantly drier than Virginia, it was also significantly colder. I camped each night above 10,000 feet, with lows into the mid to high 40s to see how the bag performed at the lower end of the 45-degree rating.


eraLoft Hollow Fiber Synthetic Fill
Thermarest Space Cowboy

This photo illustrates the lofting ability of the synthetic fill. It doesn’t look like much, but it does perform.

Therm-a-Rest claims this fill is both warm and water resistant. At first, the bag doesn’t seem to “loft” much when you pull it out of the included stuff sack. Don’t let that fool you. I used the bag during a rainy week on the Appalachian Trail because I wanted to test the water-resistant properties of the synthetic fill. The Space Cowboy sleeping bag was completely dry each morning, despite some moisture seeping through the tent floor and hanging around on the walls of the tent. It definitely passed the moisture test.

SynergyLink Connectors:

The Therm-a-Rest Space Cowboy bag comes with two “connectors” to hold the sleeping bag in place. They connect the bag to your sleeping pad. While this is a novelty, I’d just as soon not have these to worry with. I did not take them on any of my overnight backpacking trips.

Other features

This bag has a snag-free zipper, which seems to work as well as any snag-free zipper ever does. I didn’t have any trouble zipping or unzipping the bag. It has a deep hood, which is cinchable to increase warmth, and has a snap at the chin. This snap is necessary if you want to keep the bag completely zipped. I noticed that if I didn’t use it, the bag would slowly unzip throughout the night as I moved around.

The Space Cowboy is designed with a thermoreactive liner on the top side of the bag that traps heat. It also utilizes “zoned insulation” to increase efficiency. This means 65% of the fill is in the top side and only 35% on the bottom. This construction saves weight and space, since you’ll theoretically have a sleeping pad for bottom insulation. With these features, the bag is rated to 45 degrees F, with Therm-a-Rest claiming a comfort rating down to 52 degrees.


Therm-a-Rest Space Cowboy

Image via

For its weight, the temperature rating on this bag is pretty good, and seems to be fairly accurate. Therm-a-Rest advertises this as a summer bag. I’m confident in its ability to keep me warm down into the low to mid 50s, even in wet, humid conditions. I likely wouldn’t use it during an Appalachian Trail spring or Rocky Mountain fall. However, you could push the limits of summer a bit, especially with proper layering or a bag liner.

The Space Cowboy is advertised as a great bag for “cowboy camping,” or camping without a shelter. Due to the presence of hordes of mosquitoes on both of my trips, I did not truly cowboy camp in this bag. I do think the Therm-a-Rest Space Cowboy is exactly what someone who wants to cowboy camp would be looking for: the synthetic fill and water-resistant properties would keep you dry, without a shelter, even in relatively humid climates.


The feature I was most impressed with while using the Space Cowboy bag was its warmth. Considering how little it seems to loft and how thin and lightweight it is, I wasn’t expecting comfort at temperatures below 60 degrees. I was proven wrong! During my Virginia trip, I did not get cold in this bag and never felt a chill from either the top or bottom, even when temperatures dropped down into the 50s. While in Colorado, with temps creeping into the mid-40s at night, I did get chilly at night. After a couple of nights I added a sleeping bag liner, which increased the warmth enough to be comfortable. 

This bag is highly packable and takes up almost no room in my pack. I was amazed at how much extra space I had compared to my usual kit. I think this bag will become my go-to summer insulation from here on out. For a mummy bag, I felt it was pretty roomy. I usually avoid mummy bags due to feeling, well, like a mummy in them. However, I was able to move around, roll over, and adjust easily inside this bag without feeling cramped.

Finally, the bag seems to be made of exceptionally high-quality materials. I inspected the seams and sewing after each trip and have seen no signs of wear or unraveling. Despite being lightweight, the bag feels sturdily constructed and seems like it will hold up to several seasons of use.


The biggest critique I found with this bag are the extras. Marketed as “fast and light,” the intended market for this bag is someone who wants to cover a lot of ground quickly. The included pad connectors will see little use with a serious backpacker.

The bag also has small plastic attachment points. Therm-a-Rest describes these as being used to integrate this bag with their other quilts and bags for layering purposes. However, a bag or quilt with the appropriate temperature rating for the environment is always going to be lighter and more compressible than carrying multiple items. This, again, seems like an unnecessary feature. Aside from nixing these two things, the bag functioned as advertised. I could not find any flaws or drawbacks in design, durability, or function. 

Overall Thoughts of the Therm-a-Rest Space Cowboy

For the price, I don’t think this bag can be beat. It’s lightweight, packable, and affordable. It functions as advertised, working well in a variety of climates as long as you stay within the intended temperature comfort range. I would recommend this bag to anyone doing summer section hikes or backpacking trips. It also has potential with thru-hikers looking for an affordable, high-quality summer-weight bag to swap out to.

Shop the Space Cowboy Here

Disclosure: This product was donated for the purpose of review

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