Forclaz MT500 Silk Sleeping Bag Liner Review

Overview

The Forclaz MT500 is Decathlon’s entry into the silk sleeping bag liner market — a mummy-cut, 100% silk sheet designed to keep your sleeping bag clean, add a touch of warmth, and pull double duty in hostels or mountain huts. At 110g and 0.5L packed, it competes directly on weight with the category’s better-known names while landing at a noticeably lower price. It’s aimed squarely at budget-conscious trekkers and thru-hikers who want the hygiene and comfort benefits of silk without paying a premium.

Key Specs

Spec	Value
Weight	110 g
Material	100% silk
Shape	Mummy (sarcophage)
Dimensions	220 × 77 cm (head) / 54 cm (foot)
Packed Volume	0.5 L
Includes	Attached stuff sack
Care	Machine wash, max 30°C; no tumble dry, no iron
Claimed Temp. Boost	~1.5–2°C
Comparison	See how Forclaz MT500 Silk Liner compares to similar gear

Performance

Thermal Contribution

Don’t buy this expecting serious warmth extension. Forclaz claims the liner adds approximately 1.5 to 2°C to your sleeping bag’s thermal performance — and that aligns with what independent testing tends to find for pure silk liners generally. Silk liners realistically add around 1–2°C of warmth, while silk-synthetic blends with Thermolite can push 2–3°C — these are modest boosts that take the edge off, not dramatic temperature increases. The MT500 is a hygiene and comfort liner first. Use it that way and you won’t be disappointed.

Fabric Feel

The silk is functional but noticeably economy-grade. As far as silk goes, it’s not exactly the finest — it’s about the most coarse silk you’re likely to encounter in the category. If you’re used to sleeping in silk shirts, manage expectations. That said, it’s still softer and more breathable than any polyester liner at this weight, and it does what silk is supposed to do: it stays comfortable across a wide temperature range.

Fit and Cut

Here’s the main usability issue. The liner is shaped for a mummy bag and has a very high seam and narrow footbox — for someone around 6’3” (190 cm), it’s quite hard to move around and adjust. At 220 cm long and 54 cm at the foot, the dimensions work fine for average-height sleepers, but taller or broader hikers will feel the squeeze. If you’re over 185 cm, I’d try it in-store before committing. The mummy cut also means it’s not great as a standalone sheet in a warm hut — that narrow footbox gets claustrophobic fast.

Stuffsack Design

One legitimately clever detail: the stuff sack is woven to the liner itself, so it can’t go missing easily. Small thing, but I’ve lost more stuff sacks on trail than I care to admit. The 0.5L packed size is genuinely compact — it disappears into a pack hip-belt pocket without discussion.

Durability

The official spec lists reinforced stitching to reduce tearing and reinforcement at the junction — the high-stress points where silk liners typically fail first. However, some users report their Decathlon silk liner shredded after what feels like not many years of use. Silk is inherently fragile, and Decathlon themselves caution that silk is a natural and fragile material — you need to be careful when entering and exiting the liner to avoid exposing the stitching to stress. Treat it gently and it should last several seasons; yank your way into it after a long day and you’ll be testing those reinforced seams sooner than you’d like.

A Note on Composition Claims

Worth flagging: at least one user who purchased this liner reported that, after checking the care label post-purchase, the stated composition was significantly lower silk content than the advertised 100%. Decathlon’s official product page consistently lists 100% silk across all markets. It’s unclear whether that was a labelling error on a specific batch or a regional variant — but if the material spec matters to you, check the label when yours arrives.

Hygiene and Bag Protection

This is where the MT500 earns its place in a pack. Sleeping in a liner protects your sleeping bag and makes it easier to maintain — less washing equals better durability and thermal performance over time. Using a liner means washing your bag annually instead of monthly, potentially extending its useful life by years. At this price and weight, the liner essentially pays for itself in deferred bag-washing costs and preserved loft.

Sustainability

Textile dyeing requires a lot of water and produces waste water from dye baths — to reduce this impact, Decathlon chose a “two-tone” dye process for the cover, which dyes only one thread out of two.

It’s a small but noteworthy manufacturing choice.

Pros & Cons

Pros

• At 110g, it’s lighter than the Cocoon offerings, which come in at 160g — a meaningful 50g saving
• Attached stuff sack is a practical detail that competitors skip
• 0.5L packed volume is genuinely pocketable
• Very affordable entry point for a silk liner
• Comfortable and breathable for its price tier; silk is a much nicer and lighter material than polyester alternatives
• Includes a hood that fits into a standard mummy bag
• Machine washable (30°C)

Cons

• Coarse fabric hand — noticeably less refined than premium silk options
• Tight mummy cut is restrictive for taller or broader sleepers
• Modest 1.5–2°C warmth claim; Cocoon advertises up to 5.3°C from their silk liners
• No closure at the shoulder opening; the lack of a button or fastener to close it is a recurring complaint
• Durability is the category’s Achilles heel — silk needs careful handling
• Only one option in terms of shape and fabric — no rectangular, no ripstop version

Who Should Buy This

This liner is a strong match for budget-conscious hikers and travellers of average height who want silk’s hygiene and temperature-regulation benefits without the Cocoon price tag. It’s well-suited to multi-day treks where you’re sleeping in mountain huts or shared shelters, shoulder-season trips where you want a light buffer against a slightly-too-cold bag, and anyone trying to stretch the life of an expensive down sleeping bag. If you’re on a tight budget, it’s a solid and durable enough option that holds up to regular use. Taller hikers above 185 cm should consider trying it before buying, or look at options with a more generous cut.

Verdict

The Forclaz MT500 does the fundamental job of a silk liner — protecting your bag, adding a whisper of warmth, and packing to almost nothing — at a weight and price that’s hard to argue with. The fabric hand is economy-grade and the mummy cut is unforgiving for larger frames, which keeps it from threatening Cocoon’s top spot. But if you’re looking for a capable, no-frills silk liner and don’t need anything fancy, this is a sensible place to spend your money. Rating: 6.5/10.