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Mountain Hardwear Hyperlamina Spark 35 Review

The lightest 35F synthetic bag we know of; it's 3 ounces lighter than the 20F Hyper Cat, though the Spark is significantly more compressible
Mountain Hardwear Hyperlamina Spark 35
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Price:  $220 List
Pros:  Packed size, one of the lightest synthetic bags out there, center half-zipper, cozy feeling interior fabric
Cons:  Insulation isn't super long lasting, a little on the colder side of 35° bags
Manufacturer:   Mountain Hardwear
By Ian Nicholson ⋅ Review Editor  ⋅  Jun 3, 2017
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  • Warmth - 20% 6.0
  • Total Weight - 20% 6.0
  • Comfort - 20% 7.0
  • Packed Size - 15% 7.0
  • Versatility - 15% 6.0
  • Features & Design - 10% 8.0

Our Verdict

Mountain Hardwear discontinued the Hyperlamina Spark in the Spring of 2019.

This is a remarkably light synthetic bag. The Hyperlamina Spark is significantly lighter and more compressible than most comparable synthetic bags on the market. It is even smaller and lighter than many down bags currently available. When you see it in its stuff sack, most folks are surprised to see a synthetic bag; this bag packs down SMALL!!! It does share the same longevity disadvantage as most synthetic bags, where its synthetic fibers will break down much more quickly than down, resulting in a lower quality of insulated over time. However, when compared to treated down, Mountain Hardwear's synthetic insulation (Thermal Q) blows treated down out of the water, drying in roughly 20% of the time as treated down.

Our Analysis and Test Results

Performance Comparison

The HyperLamina Spark 35 is rated in the US market as a 35° F bag...
The HyperLamina Spark 35 is rated in the US market as a 35° F bag, but you'll see 32° F all over it because that's its EU Lower Limit Rating. In our tests, it was pretty comparable to most 35° F bags. You'd have to layer up if you wanted to use it in temperatures much colder.
Credit: Ian Nicholson


The Hyperlamina Spark 35 is rated at 35°F for their US market, despite being labeled as a 32°F on most of its attached literature (and its storage and compression sack). This is because it has an EU Temperature Limit of 32F (or the EU's Men's Temperature Rating). Overall, we found that this bag was pretty average in warmth among both 35°F synthetic or down bags. In our side-by-side testing, the Spark 35 wasn't as warm as any of the 30°F models, but also wasn't FAR colder than most 35°F models.

We do think if your body temperature runs low, this bag might only be good to 40°. Mountain Hardwear uses an insulation called Thermal Q, with a 60-gram layer. What does that mean? Thermal Q is a proprietary insulation made by Mountain Hardwear and used in several models of their sleeping bags and jackets. It is one of the lighter and more compressible synthetic fabrics but is slightly less long lasting than other synthetic materials.

The Hyperlamina Spark 35 offered pretty average warmth for a 35F bag...
The Hyperlamina Spark 35 offered pretty average warmth for a 35F bag but you'd certainly want to add layers for anything colder.
Credit: Ian Nicholson

If you're after a warmest synthetic bag be sure to check out the new The North Face Hyper Cat which is rated to 20°F and while not super warm for its temperature rating is noticeably warmer than the Spark. The 30°F Western Mountaineering Megalite and the Patagonia 850 Down 30 are both warmer, lighter and slightly more compressible down options.


At 1 pound 12 ounces, the Spark 35 is one of the lightest synthetic bags on the market for its temperature rating. If you frequently camp in wet environments, where it would be best to take a synthetic bag then the Spark is though to beat. It is worth noting that The North Face Hyper Cat is only 2 ounces heavier, though the Spark is far lighter than most other synthetic models including the mega classic 20-degree Cat's Meow (2 lbs 5 oz). The REI Co-op Igneo 25 is similar in price, but is down, and weighs 1 pound 10 ounces.

Part of the reason the Hyperlamina is so light is its high-quality synthetic fill, fairly low-weight 22D nylon shell, and half-length zipper; the zipper shaves 2-3 ounces off versus using a full-length zipper. Even compared with closely rated down bags, the Spark 35 doesn't give up much; in fact, it's lighter than the Kelty Cosmic. Basically, it's one of the lightest 30-35°F synthetic bags that are currently available.

The Hyperlamina Spark 35 (far left) compared with several other...
The Hyperlamina Spark 35 (far left) compared with several other performance oriented bags. As you can see the Spark 35 compresses extremely small by any account but especially for a synthetic bag. The Spark 35 (far left) compared with several other bags, from left to right: The Nemo Salsa 30 (second from left), REI Igeno (center), Marmot Hydrogen, and Western Mountaineering MegaLite.
Credit: Ian Nicholson

Packed Size

Besides being one of the lightest synthetic bags, the Spark 35 is also easily one of the most packable options (of its temperature rating) on the market today. Check out the chart below to see where this bag scored in Packed Size compared to its competition.

The Spark 35 packs down smaller than several down bags like the Kelty Cosmic Down 20, and is even comparable to performance-oriented bags like the Western Mountaineering MegaLite, Patagonia 850 Down 30, and Marmot Phase 20, though it's around 15-20% bigger than those models. The Hyperlamina Spark 35 is definitely smaller than the The North Face Cat's Meow, but less so with the 2018 update to the Meow..

The sweet included compression stuff sack that comes with the...
The sweet included compression stuff sack that comes with the Hyperlamina Spark. We thought this compression sack was well-sized, minimizing the packed size of the bag.
Credit: Ian Nicholson

We love that the Hyperlamina Spark 35 comes with a very functional compression sack, in addition to the storage sack. The compression sack fits the bag very nicely and helps to minimize the amount of space that this bag will take up in your pack.

The Hyperlamina Spark 35 offers internal dimensions that are on the...
The Hyperlamina Spark 35 offers internal dimensions that are on the wider side of mummy-style bags in our review. Here the Spark 35 (top) compared with the Sea to Summit Spark III.
Credit: Ian Nicholson


The Spark 35 offers wider than average dimensions compared with most backpacking-oriented mummy-style bags in our review and on the market including the Hyper Cat. It offers near identical dimensions as our Editors' Choice the Western Mountaineering MegaLite and was one of the more comfortable bags that we tested. While it offered fairly spacious dimensions, we never felt like the bag was too big; in the case of a bag being too big, cold spots have the potential to be created. We did not face this issue when using the Spark.

Most side and tummy sleepers could get their knee pretty high while sleeping in this bag. We found it to offer a high level of comfort among contenders we tested, especially for those who sleep in positions other than on their back. The Spark 35 features a comfortable 22D fabric for its lining, which was above average for its feeling against our skin. We liked the interior fabric of the Spark 35 better than the Cat's Meow.

The Mountain Hardwear Hyperlamina Spark 35 (left) is on the wider...
The Mountain Hardwear Hyperlamina Spark 35 (left) is on the wider side and its dimensions are close, but weren't quite as big as The North Face Cats Meow (center) or Kelty Cosmic Down 20 (right).
Credit: Ian Nicholson


This is a fairly versatile bag. It's spacious enough for car-camping, light enough for most backpacking trips, and its synthetic fill helps it excel in both wet and dry climates. The half-zipper offered plenty of ventilation; slightly to our surprise, we never felt it was a hindrance during our real-world testing.

We do think that in warmer weather, the Hyperlamina might be a bit more difficult to use as a blanket, as you can't open it all the way up. In temperatures that dip below 35°F, the Spark offers plenty of shoulder space, which allows the user to wear additional layers. The Western Mountaineering Megalite and Ultralite were some of the most versatile bags in our review.

The Hyperlamina Spark 35 is a pretty no frills bag, instead focusing...
The Hyperlamina Spark 35 is a pretty no frills bag, instead focusing on minimizing weight and comprehensibility. The Spark 35's half length zipper saves a few ounces over a full-length zipper and offers enough ventilation to be used in a wide range of overnight temperatures. In fact, our testers loved the center zipper because it was so easy to get in and out of the bag.
Credit: Ian Nicholson

Features and Design

The Hyperlamina doesn't have a lot of extra features, as its design focuses on low weight and compressibility. Its half-length zipper shaves off a few extra ounces and we enjoyed that it was in the middle, versus having a less useful zipper of the same length on the side. We hadn't used many center zip style sleeping bags previously and were a little skeptical; however, after several days in the field, nearly all of our testers loved the design. It's just plain easier to unzip, sit up in, and perform daily activities in. The hood is basic, yet well-designed, and is effective and comfortable. The Sea to Summit Spark III offered more features and a better overall design.

The synthetic fabric used in the Hyperlamina is super lightweight and compressible, but is slightly less durable than other synthetic fabric; it will likely lose around 20% of its warmth when you hit the five-year use mark.

Hyperlamina 35 Versus Treated Down Bags

Water-resistance and drying times were pretty similar for the treated and non-treated down bags we tested. Synthetic fabrics performed far better, taking about 20% off the times of hydrophobic down in the soak test.

The Hyperlamina Spark 35 is a super versatile bag; it's spacious...
The Hyperlamina Spark 35 is a super versatile bag; it's spacious enough for car camping and shorter trips, and is also light and compact enough for long range adventures. It vents decently well, but is roomy enough in the shoulders to add extra layers on 30 F and below nights.
Credit: Ian Nicholson

Best Applications

The Spark 35 is probably the best summertime 3-season backpacking synthetic bag we have seen. We remain amazed by its low weight and fantastic packed size, as it's comparable to average and slightly above average down bags in many ways. If you want a warmer bag to use regularly around 30°F and below, we'd go for Hyper Cat for backpacking or climbing or The Cats' Meow for occasionally backpacking or car camping trips as both are noticeably warmer and rated to 20°F.


At $220, the Hyperlamina Spark 35 is comparable in weight and packed size to that of many down bags with 700+ or lower down fill power. That said, it is also comparable in price to many of those bags and it likely won't last as long, because synthetic fibers break down far quicker (than down), losing their warmth.


The Spark is among the highest synthetic bags available. We do think if you're apprehensive about the Spark's 35-degree temperature rating, which we think most folks will need to wear a jacket in under 40F, then check out The North Face Hyper Cat which is only a few ounces heavier but noticeably warmer.

Ian Nicholson
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