Therm-a-rest Parsec 20F/-6C Sleeping Bag | Review - Outdoors Magic

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Therm-a-rest Parsec 20F/-6C Sleeping Bag | Review

A water repelling and sustainably crafted down sleeping bag for fast and light missions during spring, summer and autumn

Why We Chose the Therm-a-rest Parsec™ 20F / -6C: Sustainable, packable, comfortable

The newly updated Parsec is a mummy shaped, down filled sleeping bag designed for 3-season performance in the great outdoors. Boasting solid eco-credentials and a raft of features, this award-winning bag from Seattle-based sleep system experts Therm-a-rest has pretty much everything you could want from an expedition bag. Therm-a-rest have also recently unveiled a -18C and a 0C version, so there’s now a Parsec sleeping bag whatever your preferred camping season.

Who is the Therm-a-rest Parsec™ 20F / -6C for?

The -6C temperature limit of this model makes it highly suitable for three season use. Looking specifically at its UK suitability, we’d say it’ll really suit campers who are looking for something they can use right through the year, except on cold winter nights and some of the colder nights at the end of autumn and start of spring.

Again, from a UK perspective, its water repellent and fast drying qualities make it suitable for the wet conditions often found here, while its goose down fill means that has a strong weight-to-warmth ratio that should appeal to backpackers, fastpackers and just anyone who likes kit they can carry on multi-day adventures.

Its down is highly compressible, meaning it packs down smaller than its synthetic counterparts too. Features like sleeping pad attachment points and its integrated pocket add useability, while the long zip pulls on its anti-snag zippers are a nod to glove use in the shoulder seasons.


When it comes to sleeping bag filler, down is the most sought-after material due to its remarkable thermal qualities, low weight and its compressibility. The Parsec boasts 800-Fill hydrophobic down that absorbs 90% less water and dries three times quicker than untreated down, which is a blessing if you’re camping somewhere like Skye or North Wales, where it can rain solidly for days.

Its high 800 fill power makes for large down clusters, giving it a solid warmth to weight ratio, important for those early spring wild camping trips when winter still has a tenuous grip on the land. Down is a natural product, in this case harvested from geese. Responsible manufacturers like Therm-a-rest go to great lengths to ensure their down is sourced ethically – the Parsec is Responsible Down Standard Certified, giving you peace of mind that the waterfowl in the supply chain were treated well.

The Parsec also gets a tick for using certified 100% recycled ripstop nylon in both the shell and the lining fabric.


Warmth is the most important measure of performance for a sleeping bag and the Parsec is designed to keep you cosy beyond freezing point. Cold spots are kept to a minimum with its boxed baffles, while zoned insulation means that 60% of the down is contained in the top of the bag, keeping you warm on those chilly early mornings. It’s our extremities that suffer the most during cold wild camps; the Parsec aims squarely at achieving toasty toes with an insulated foot warmer pocket.

The -6C in the name refers to its temperature ‘limit’, defined by the European Norm temperature rating system as the level at which an adult male can sleep relatively comfortably for eight hours without waking. This means that the Parsec will perform reasonably well when the mercury tumbles into negatives but it’s not a bag for full-on winter camping or high-altitude expeditions.
It’s worth stating that this isn’t the only bag in the Parsec series. Campers less fussed about the shoulder seasons can opt for the 32F / 0C model, while winter warriors may want to consider the highly insulated 0F / -18C option.

Tester’s Verdict

Grant Hyatt, North Wales based outdoor photographer 

“My sleep system has been fairly settled for a few years, I’ve been really happy with the weight and warmth of my current sleeping bag. But then I tried this. The temperature ratings speak for themselves, so I won’t comment on that and I’ve only been out in this at circa 3/4 degrees, so there’s plenty left in the tank to use it in the milder winter months. I think what looks to set this apart is a few simple, yet incredibly effective features.

“Really chuffed to now have this sleeping bag in my kit stash.”

“The first one I noticed was an exterior pocket, for your keys or as I used it, a camera battery. Having it on the outside just makes life a load easier when trying to retrieve them. The other, was the few options for securing the sleeping bag to the sleeping mat, which if you toss and turn through the night, has meant that you wake up with the bag in largely the same position as you started. That wiggle in the morning as you try to orient the sleeping bag zip next to it’s starting point can be a frustrating, though occasionally amusing experience.

“The last feature I noted was the anti snag covering on the zip. I didn’t notice it at first and initially just the lack of snagging down to luck, but once i spotted it I had a good go at trying to get the zip to snag. But failed, every time. Really simple, incredibly effective. Really chuffed to now have this sleeping bag in my kit stash.”

Therm-a-rest Parsec 20F -6C

Selected for the Outdoor 100 2022/23
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