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Photo credit: Fiona Russell.

Mountain Hardwear Hyperlamina Spark 35 sleeping bag review


Last updated: 16-Aug-18

By Fiona Outdoors

Many ultra runners will have a need for a lightweight but warm sleeping bag. This is the only synthetic bag in our testing collection and Mountain Hardwear claim it is “engineered to be the lightest and warmest synthetic bag available”.

The type of sleeping bag that you buy will depend on when and where you will be using it. Most sleeping bags are rated according to their ability to keep the average person warm in a particular air temperature range. The Spark is rated 5ºC for comfort and a lower limit of 0ºC.

Because I get cold easily, I would use the bag in conditions no less than 5ºC but most likely between 5ºC and 10ºC. This means it is a sleeping bag that I would use in the summer in the UK. The average person could use the bag on cooler spring nights and maybe even early autumn.

Mountain Hardwear Hyperlamina Spark 35 - Features

  • Synthetic fill
  • Comfort temperature: 5ºC
  • Temperature limit: 0ºC
  • Two lengths, regular or long
  • Proprietary welded Lamina construction to “enhance loft and eliminate cold spots”
  • Zoned insulation to “maximise warmth where it's needed most”
  • Thermal Q insulation for “outstanding compressibility and to maintain excellent loft”
  • Single half-length centre zip with dual sliders
  • Performance mummy cut is “snug, reducing girth weight and bulk but maximises thermal efficiency”
  • Comfort footbox
  • Ultralight shell is soft and highly wind resistant
  • Face gasket and tailored hood
  • Compression stuff sack: 15 cm x 33 cm
  • Weight: 788g
  • RRP £180

Photo credit: Fiona Russel.

Pros: What’s good about Mountain Hardwear HyperLamina Spark 35

This is a lightweight synthetic sleeping bag. At a shade under 800g it is a lot lighter than many bags on the market and at a reasonable price.

It also has synthetic fill, which can be an advantage over down because it will keep you warm even when wet or damp. Many brands do get around the concerns of useless wet down by adding water-resistant outer fabric or filling with water-repellent treated down.

Inevitably, however, on extended trips bags can become damp and so a synthetic fill gives peace of mind. I find that synthetic holds its loft for longer when compared to down but it does depend on how you care for your sleeping bag.

(Note: Never store sleeping bags for a long time in their small stuff bag. Use a large storage bag if it comes with the bag or store unpacked.)

The bag is warm for its weight. I have tested warmer bags that weigh less but the price tag is favourable and if you can cope with a few extra hundred grams in your bag you’ll like this bag.

Mountain Hardwear use what they call Lamina Technology – combined with Thermal Q insulation – to maximise and maintain loft while also giving good compressibility when stored in the sleeping bag stuff bag.

The bag does feel fairly puffy and warm. Synthetic rarely feels as light and puffy as down but I do like the quality feel and weight of this synthetic fill bag.

The stuff bag has useful compression straps to minimise its size and I have not seen a synthetic bag that offers good warmth being compressed to such a small size. 

The sleeping bag also has several great features. The half front zip helps with getting in and out of the sleeping bag and if you get warm in the night you can zip it open. The zip works from the top and bottom for extra versatility.

The hood and collar are generous and can be toggled tighter for a neat fit around the head with an elastic drawstring. The top of the zip has a cover (“gasket”) so it doesn’t irritate your face or chin.

The width and length of the bag is generous. For larger people this will be a bonus.

The yellow and orange colourways are also fantastic. Let’s have more sleeping bags that are brightly coloured!

The bag does as it says it will in terms of warmth and comfort. I found the synthetic loft to be adequate for a cool summer’s night of camping.

Photo credit: Fiona Russell.

Cons: What’s not so good about Mountain Hardwear HyperLamina Spark 35

The blurb claims the bag is “engineered to be the lightest and warmest synthetic bag available”. This is a bit vague as in “available” where?

The bag does feel fairly light but it’s not the lightest on test. The synthetic fill is also obviously synthetic. There are advantages to synthetic but, on balance, I prefer a down fill bag, as long as it can be protected against damp and wet.
Down feels cosier and warmer.

In contrast, my partner is adamant he prefers a synthetic bag because he says all down bags he has slept in end up damp even when made with water-resistant fabric. So, I guess, it’s a matter of personal choice.

Saying that, if budget is important to you a lightweight and warm sleeping bag for around £150 is a great buy. Some people are allergic to down, too, so synthetic is a good compromise.

The generous sizing is a bit too generous for someone like me. Even the “regular” is bit too roomy and I’d prefer a slimmer fit bag that would also weigh less.

I wasn’t aware of the warmth zoning areas but I stayed generally warm so they must have worked because I would normally get cold feet in the night and I didn’t in this bag.

A water-resistant treated outer fabric would add to this bag but for the price it’s fine without it.


If budget is important and you want a fairly lightweight yet warm summer sleeping bag, this one is a good choice. It is synthetic, rather than down, and offers generous roominess if you are on the large size. It packs down neatly for a synthetic bag.

Design 8/10
Features 8/10
Performance 7.5/10
Value 9/10
Total 8.1/10


Other sleeping bags you may want to consider:

PHD Minim 400 K sleeping bag
Mountain Hardwear women’s Phantasia
Alpkit PipeDream 400 down sleeping bag
Rab Neutrino 400

About the writer: Fiona is a keen runner, preferring off-road and hilly to flat and road. She lives in Scotland where the weather is fickle so needs to be prepared for all conditions.

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