Reviews You Can Rely On

Klymit KSB 35 Review

Lightweight and packable, but minimal insulation
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Klymit KSB 35 Review
Credit: Klymit
Price:  $190 List
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Manufacturer:   Klymit
By Jack Cramer ⋅ Review Editor  ⋅  May 19, 2019

Our Verdict

The KSB 35 is a one size fits all sleeping bag with an enticing price. It's every bit as lightweight and packable as advertised. The longer than full-length zipper also gives you more venting possibilities and the option to unzip it into a quilt. Our testers, however, were less than impressed with its insulation and a temperature rating that seems severely exaggerated. The KSB 35 is still a nice bag, but we can only recommend it for use in the warmer summer months.
Extra-long zipper
Packs small
Unzips into a quilt
Colder than its warmth rating
No draft collar or stash pocket
Unpleasant smell
Product Revamped
Klymit changed some things about the KSB 35 since our test cycle. We go into more detail and show comparison photos below.

Our Analysis and Test Results

Updated Dual Fill KSB 35

Klymit redesigned this bag. Where it was all 650-fill down before, the updated version features 650-fill down on the top while lofting out the bottom with synthetic filling. The new bag also uses stretch baffles and a Length Lock technology that allows you to shorten the bag if necessary. Compare these versions below — the model we tested is pictured first, followed by the new KSB in the second photo.

Take note that because we haven't tested the updated model, the review below is still our account of the older version. However, we're linking to the updated model since it's more likely to be in stock.

Hands-On Review of the KSB 35

In the detailed review below, we challenge several marketing claims made on the Klymit website, including the KSB 35's temperature rating and advertised features. While we were disappointed with these problems, the team at OutdoorGearLab is in no way suggesting intentional dishonesty on behalf of Klymit. Rather, it's more likely an instance of different sleeping bag versions (0F, 20F, and 35F) mistakenly listed with the same features.

klymit ksb 35 - the ksb's best feature might be its longer than full-length zipper...
The KSB's best feature might be its longer than full-length zipper. Here, two testers comfortably share a single bag that's been fully unzipped into a quilt.
Credit: Drew Smith


The KSB 35 is advertised with an EN lower limit rating of 21°F. Our reviewers believe this is extremely inaccurate, and its warmth is more comparable to the average bag with a 35F rating. In our warmth test, the lead tester got a chill while sleeping overnight in a 48F room with a great sleeping pad (R = 4.6).

klymit ksb 35 - check out the difference between budget down and ultra-premium. the...
Check out the difference between budget down and ultra-premium. The 850+ FP down of the Western Mountaineering MegaLite (right) lofts 6 inches upward, while the cheaper 650 FP down of the Klymit KSB 35 (left) lays nearly flat on the ground.
Credit: Jack Cramer

For comparison consider that this bag doesn't have a draft collar and is filled with 14.1 ounces of 650 fill power down. The Rab Mythic 400, in contrast, is a premium sleeping bag with an identical temperature rating, but its 14.1 ounces of down are much higher quality (900 fill power), and it has a draft collar.


This one size fits all bag weighed in at an impressive 1.91 pounds on our scale, making it one of the lightest bags in our budget review. The only problem, however, with this impressive performance is that the KSB 35 doesn't provide enough warmth for us to consider it a true 3-season sleeping bag. It thus exhibits an impressively low weight, but a weight that's unfair to compare with the other bags in this review.

klymit ksb 35 - shorter folks sleeping in this one size fits all bag can use "length...
Shorter folks sleeping in this one size fits all bag can use “length locks” to shorten the length of the bag. These are effective but you end up carrying the additional weight of a bag that's unnecessarily long.
Credit: Jack Cramer


The KSB 35 has average dimensions for a budget sleeping bag. These dimensions will probably feel spacious enough for people that don't mind sleeping in mummy bags, but constrictive for those that do not. Our testers don't like the hood closure because it uses an inelastic drawstring that can put pressure on your head when closed tightly. Some of our testers also complained that this bag had an unpleasant smell for the first few months out of the box.

klymit ksb 35 - the ksb 35 packed inside the simple nylon stuff sack that it comes...
The KSB 35 packed inside the simple nylon stuff sack that it comes with.
Credit: Jack Cramer

Packed Size

In our compressed volume test with an after-market compression sack, the KSB 35 packed down to 7.0 liters. This figure would be tiny for a 3-season bag, but we don't consider this bag warm enough for 3-season use. Compared to an ultralight sleeping bag that provides a similar level of warmth, it doesn't pack particularly small.

klymit ksb 35 - the ksb 35 is one of the few bags that lets you unzip all the way...
The KSB 35 is one of the few bags that lets you unzip all the way around the foot of the bag.
Credit: Jack Cramer


Our favorite feature of the KSB 35 is its longer than full-length zipper. This zipper starts near the head of the bag on the left side, wraps around the foot of the bag, and ends near the foot of the bag on the right side. Because it's a two-way zipper, you have the luxurious option to vent only your feet. You can also unzip it all the way and turn the bag into a quilt. This feature greatly extends the upper end of the temperature range in which the bag can comfortably be used.

klymit ksb 35 - unfortunately, the hood drawstring is inelastic string which isn't...
Unfortunately, the hood drawstring is inelastic string which isn't all that comfortable when the hood is fully tightened.
Credit: Jack Cramer

Features and Design

We're big fans of the zipper's extreme length, and also the Y-shaped slide it incorporates to prevent snags. Unfortunately, the KSB 35 is only available in one size that accommodates sleepers up to 6'6". For shorter folks, there are “length locks” near the foot of bag that you can use to shorten the bag temporarily. These are effective but not ideal for long-term use. After all, most bags are available in size short — around 66 inches in length. If you're under 5'6" and settle for the one size fits all KSB 35 you'll have to carry around the additional weight of an entire foot of down and nylon for the lifetime of the bag.

klymit ksb 35 - the ksb has a y-shaped anti-snag zipper slide. dual pull tabs make...
The KSB has a Y-shaped anti-snag zipper slide. Dual pull tabs make opening the bag in the dark a lot easier.
Credit: Jack Cramer

We also have a few concerns about the features advertised on the Klymit website where an image of a blue KSB 35 indicates that it includes a “draft collar” and “stash pockets.” The model we tested, however, did not have these features.

klymit ksb 35 - at the left, you can see an advertisement where klymit highlights...
At the left, you can see an advertisement where Klymit highlights the KSB's “draft collar” and “stash pockets”. A supplemental video shows these features positioned near the chin of the bag on the inside. The bag that we tested, however, had neither of these features.
Credit: Jack Cramer


This bag is exceptionally light and compressible for its affordable price. Its overall value, however, is lessened due to its limited warmth. Nevertheless, if you're able to take full advantage of the ability to also use this sleeping bag as a quilt, it does provide a decent value.


The KSB 35's advertised specs are pretty impressive. Under two hundred bucks for a 1.9-pound sleeping bag that's rated down to 21°F? What a deal! Unfortunately, our testers found the bag's insulation was wasn't even sufficient to stay warm at 40°F. We're still big fans of its extra long zipper, but shoppers should be aware that this bag is better for summer, rather than 3-season use.

Jack Cramer