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Slumberjack Kepler +20°F

rated 2.5 of 5 stars

The Kepler +20°F has been discontinued. If you're looking for something new, check out the best 3-season synthetic sleeping bags for 2024.

photo: Slumberjack Kepler +20°F 3-season synthetic sleeping bag

Great bag from a good company. Contrary to popular belief, it is warm and the quality merino wool does wick moisture away from your body.


  • Merino wool
  • Comfortable
  • Packs small


  • No draft collar on the shoulders
  • Poor foot box construction

This bag is great. Merino wool is awesome to wick moisture away, and IF the bag does get wet, it dries quick. I've had this bag since spring 2008 and it's still going strong after MUCH use (car camping, backpacking, overnights, etc.).

Folks who complain about sleeping bags not keeping them warm at the rated temp just don't understand how these bags work. They insulate off of your body heat, so if you wear tons of layers of clothes that keep your body heat from reaching the bag, then you might as well not sleep in the bag. In my Kepler I have slept in ~20-30 degree F weather in shorts and a t-shirt with a good sleeping pad for insulation from the ground and been plenty warm. True story.

This bag packs down small, is warm for 3 seasons, is comfortable and just all around great for me. I get excited when I have an excuse to use it.

The only bad things I have to say are the no draft collar on the shoulders and a poor foot box construction. Not deal breakers, and I was aware of them when I bought it, just find myself sometimes saying "Man, I wish..."

Side note, I got this bag on a killer deal from back in spring 2008

Source: bought it new
Price Paid: $64-ish

20 degrees my butt. I wouldn't take this thing out if the forecast threatens to drop below 40.

I carried this bag out for a few nights of 30 degree weather, and I was supremely disappointed. I nearly froze to death in the bag; all while wearing two layers of fleece, two pair of socks, and a thick hat, too.

The short zipper is annoying, too - it only goes halfway down to the feet. It also has tendency to unzip itself if you're not careful. There's no draft collar near the neck. The bag is not very breathable - leading to a very clammy feeling bag in the morning. The bag also feels suspiciously thin, leading to a rather uncomfortable sleep without a thick sleeping pad.

On the good side, it does seem well made. It has a comfortable shape for a mummy bag. It stuffs down fairly small (although still larger than my much warmer down bags) and seems pretty light. And wasn't too expensive.

Design: mummy
Fill: fossil fuel
Temperature Rating: 20 (more like 40)

I bought this to use for dual sport motorcycle camping. I bought it because it packed down small and I could fit it in a pannier.

I give it 2 stars because it packed down small and the wool liner was nice, but other than that it was horrible. It got down to 35 camping about 200 feet from the Pacific Ocean. We were not on the sand, but it was close to the water. I used a Therm-a-rest Prolite 4 and was inside a decent tent. I froze. I think I would have been better off in my old 19.99 Coleman Walmart/Target special.

As others have said about the Slumberjack Ultimate 20 degree bag, it should be a 50 degree bag. Should have known it would not work well when it stuffed down to 7x12, wishful thinking I guess.

Price Paid: $80

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Price Historic Range: $79.99-$169.95
Price Historic Range: $164.95
Reviewers Paid: $64.00-$80.00

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