Wild CampingSimondSleeping Bag
Simond MT900 5°C sleeping bag review: brilliant bang for your buck
Previously branded as Forclaz. If you’re after a lightweight down sleeping bag that doesn’t break the bank, the Simond MT900 5°C is an absolute gem.
✓ Best BuySimond MT900 5°C Down Sleeping Bag
Weight830 gFill power700 FPPrice£149.99
The good✓ Amazing bang for your buck
✓ Very lightweight and warm
✓ High-quality down insulation
✓ Packs down very small
✓ Included compression sack is excellent
✓ Great zips
The not-so-good✗ Sarcophagus cut might take some getting used to
Buy from Decathlon →
At a glance
| Brand | Simond (Decathlon) |
| Model | MT900 5°C Down Sleeping Bag |
| RRP | £149.99 |
| Weight | 830 g (size Large) |
| Fill | 700 CUIN, 90% grey duck down |
| Comfort rating | 5°C |
| Limit rating | 0°C |
| Packed size | ~Melon-sized with compression sack |
| Ideal for | 3-season backpacking, wild camping, thru-hiking, fastpacking, bikepacking |
| Not suitable for | 4-season use |
Simond MT900 5°C down sleeping bag review
Simond is Decathlon’s high-mountain gear brand — and while it’s not as widely known in the UK as Rab or Mountain Equipment, it’s been producing solid, budget-friendly mountaineering kit from its base in Chamonix since 1860. While historically better known for hardware like ice axes and crampons, Decathlon has recently folded its trekking-focused Forclaz range into the Simond line, creating an even broader offering for outdoor types on a budget.
The Simond MT900 5°C down sleeping bag is a lightweight, three-season down sleeping bag designed for trekking, bikepacking and wild camping in conditions from spring through to autumn. With a comfort rating of 5°C, a total weight of 830 g (in size large) and a packed size that fits neatly in a fastpack or small rucksack, it’s clearly targeting fast-and-light adventurers who don’t want to splash out on top-tier kit.
It currently retails at £149.99 — and at that price, it’s seriously undercutting premium brands while delivering specs that hold their own. Rab’s Alpine 200 comes in at 630 g and boasts a minimalist design, but it retails for nearly double the cost (£270) and uses a lower-grade 650-fill power down. The OEX Chimera EV 500 is £30 cheaper at £119 but is over a kilo in weight, doesn’t pack down nearly as well, and uses lower-quality 600-fill. With the MT900, you’re getting 700-fill down, clever baffle design, and a compression sack that genuinely compresses — all of which are rare at this end of the market.
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Our experience with the Simond MT900 after a year of use
We’ve spent over a year sleeping in the MT900. In that time, it’s been out with us on a dozen nights across the UK — including a blustery wild camp on Dartmoor’s Great Mis Tor in spring, where temperatures dropped right to the comfort limit, a balmy summer filming trip in the Brecon Beacons, and a fastpacking adventure along the Thames in early autumn, tucked into the bottom of an Ultimate Direction Fastpack 30. Each time, we paired it with a good-quality mat and occasionally added layers depending on the chill.
What we found, each time, was a bag that managed to walk the fine line between bulk and warmth remarkably well. While it took some getting used to the snug cut at first, we soon found our rhythm. As long as we respected the temperature guidelines and used the right mat, we stayed warm and comfortable. Even in the exposed terrain of Dartmoor, with wind slicing through the air outside the tent, we were cosy enough inside the MT900 to drift off with ease.
Standout features of the MT900
The MT900 doesn’t try to dazzle with overengineered gimmicks — instead, it delivers a solid package of thoughtful features that actually matter. Take the insulation: the MT900 contains 90% grey duck feather and 10% grey duck down, rated at 700 CUIN. For a sub-£150 bag, this is excellent stuff. The 700-fill power gives it strong loft and good compressibility, bouncing back nicely after being packed away.
Warmth and packability
Warmth-wise, the MT900 delivers what it promises. When used with a properly rated mat (we recommend an R-value of 4 or higher) and some decent layers, it provides reliable comfort right down to its 5°C rating. We’ve slept soundly in it during early spring and late autumn in the UK.
One of the real highlights is its packability, with the included stuff sack being a solid standout. Using a dry-bag-style roll-top closure, it allows you to squeeze the air out and reduce the pack size to something roughly melon-sized — ideal for fast-and-light setups where space is at a premium. The addition of a handle on the bottom is a small but incredibly useful touch, making it far easier to yank from the depths of a jammed rucksack.
The shape of the bag, described as ‘sarcophagus style’, works well in practice. It’s body-hugging for efficient warmth, but not claustrophobic unless you’re particularly broad or restless at night. The hood is soft and cocooning without feeling restrictive — fully done up, it makes a noticeable difference to overall warmth on chilly nights.
“We’ve tested bags that cost twice as much and left us colder. The Simond MT900 just works.”
Extra features
Zips are a common weak spot on affordable bags, but we had few complaints here. The zip runs smoothly with minimal snagging. Inside the bag, there is a small internal pocket — just about big enough for a phone or head torch. The cleverly-designed baffle layout is worth a mention: horizontal baffles wrap the upper body for even warmth distribution, while vertical ones around the legs and feet help keep insulation in place where it tends to shift most. You also get two hanging loops for drying and a breathable mesh storage sack for stashing the bag between trips.
Our verdictPremium warmth-to-price — one of the best-value down bags on the UK market.Over a year of testing in a range of real-world British conditions, we’ve grown to seriously rate the Simond MT900. It’s warm, packs impressively small, and doesn’t weigh you down. Most importantly, it delivers all of that at a price point that feels almost too good to be true. For wild campers, thru-hikers, fastpackers and backpackers operating on a budget — but who still want kit that delivers — the Simond MT900 is a proper no-brainer.Buy from Decathlon →
FAQs
What are the Simond MT900 sleeping bag’s temperature ratings?Comfort rating: 5°C. Limit rating: 0°C. In our testing, these ratings are accurate — respected with a quality mat and light layering, we stayed comfortable in both.
How warm is the Simond MT900 sleeping bag in real-world conditions?Very warm for a 3-season bag. In spring conditions on Dartmoor where temperatures dropped to the comfort limit, we stayed warm with a quality mat and light layers.
Is the Simond MT900 sleeping bag easy to carry in a backpack?Yes. At 830 g it packs down to roughly melon-sized using the roll-top compression sack — easily fitting in the bottom of a fastpack or rucksack.
Is the Simond MT900 sleeping bag worth the money?Absolutely. At £149.99, nothing else we know of delivers this combination of 700-fill down, clever baffle design, excellent packability and comfortable warmth at this price.