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.
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.
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).
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.
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.
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.
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.
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.
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.
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.
