Sleeping bags
Down or synthetic, when only one of the two publishes a fill power?
This is the clearest split on the shelf: a 650 fill power down bag at 760 g against a 350 GSM double-layer synthetic at 1900 g. The down bag publishes what down is judged on and leaves its packed size out; the synthetic publishes its packed size and its fill construction and leaves the fill power out, which is fair enough, since fill power describes down. Neither names a temperature standard.
| Compared on | 650 fill power down bag, 20D nylon shell | GRÖNLAND, 350 GSM double-layer mummy bag |
|---|---|---|
| Comfort rating | Above 5 °C, stated as the comfortable temperature | Around 0 °C, stated as the comfort temperature |
| Limit rating | 0 °C, stated as the limit temperature | Not stated as a limit — the title carries -23 °C and -5 °C, neither of them labelled |
| Standard quoted | None named — neither EN 13537 nor ISO 23537 appears | None named — neither EN 13537 nor ISO 23537 appears |
| Fill | Down, stated as an 85 % down fill treated to be water-repellent | Synthetic, stated as polyester in a double-layer fill |
| Fill power | 650 fill power, stated in the title | Not published — fill power describes down, and this bag is stated as polyester |
| Shell denier | 20D nylon, stated for the outer fabric and the lining alike | Not published — a rustle-free outer with a PFC-free water-repellent coating, and no yarn weight |
| Stated weight | 760 g in the medium size and 885 g in the large, given as the net weight | 1900 g, with no label saying what is counted |
| Packed size | Not published — a mesh storage bag and a compression sack are supplied, with no dimensions | 24 × 30 cm in the supplied compression sack |
| Baffle construction | Not published | Double-layer fill, stated; the baffle pattern itself is not given |
Each tick belongs to its own line and nothing more. The row of ticks is not a score: the two verdicts underneath settle the page, because these two answer different questions on the trail.
The Naturehike is the bag for anyone counting grammes: 760 g in the medium size, a 650 fill power and a 20D shell are all published, and it is the only one of the two to separate a comfort figure from a limit figure. What it never gives is a packed size, which on a down bag is half of why you paid for down.
The EXPLORER GRÖNLAND is the roomier, heavier synthetic answer, and it publishes the two things the down bag does not: a 24 × 30 cm packed size and a double-layer fill construction. Its -23 °C and -5 °C sit in the title with neither of them labelled, so the only figure you can actually read as a comfort temperature is the stated 0 °C.
Fill power measures how much volume a given weight of down expands to fill — the loft it produces per gramme. It is a property of down, so a polyester bag has no fill power to publish, and its 350 GSM fill density is the figure that plays the same role.
A comfort rating normally comes from a laboratory procedure with a heated manikin, defined by EN 13537 and its successor ISO 23537. Neither listing names either standard, so both figures are the maker's own. They are an indication of where a bag is aimed, not a measurement you can compare across brands.
Down · 650 fill power · 85 % down content · comfort above 5 °C and limit 0 °C stated · 20D nylon shell · 760 g / 885 g
The only down bag in this group: it publishes a fill power, a down content, a shell denier and a comfort and limit pair — and still names no standard.
Best for: Backpacking in mild conditions where 760 g and a 650 fill power down bag are the reason for the purchase.
≈ £116 / 110 €
Mummy · 350 GSM double-layer fill · comfort around 0 °C stated · 1900 g · 24 × 30 cm packed · 230 × 82 × 55 cm
A large mummy bag that names a comfort temperature of around 0 °C, publishes weight, packed size and a full cut, and names no standard behind the figure.
Best for: Taller sleepers camping in the cold shoulder seasons, where a 230 cm bag and a stated comfort figure matter more than carried weight.
≈ 70 €
Prices in these summaries were read on the dates each review gives. The live figure sits beside every product.
