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 (26.8 oz) against a 350 GSM double-layer synthetic at 1900 g (67 oz). 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 down sleeping bag | GRÖNLAND double-layer mummy bag |
|---|---|---|
| Comfort rating | Above 5 °C (41 °F), stated as the comfortable temperature | Around 0 °C (0 °F), stated as the comfort temperature |
| Limit rating | 0 °C (0 °F), stated as the limit temperature | Not stated as a limit — the title carries -23 °C (-9 °F) and -5 °C (23 °F), neither of them labeled |
| 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 (26.8 oz) in the medium size and 885 g (31.2 oz) in the large, given as the net weight | 1900 g (67 oz), 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 (9.4 × 11.8 in) in the supplied compression sack |
| Baffle construction | Not published | Double-layer fill, stated; the baffle pattern itself is not given |
| Listed on amazon.com | No | No |
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.
No amazon.com listing was found for this one. We hold references for other markets but none for the United States, so it may not be buyable here — which is the first thing to weigh against anything below.
The Naturehike is the bag for anyone counting grams: 760 g (26.8 oz) 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.
No amazon.com listing was found for this one. We hold references for other markets but none for the United States, so it may not be buyable here — which is the first thing to weigh against anything below.
The EXPLORER GRÖNLAND is the roomier, heavier synthetic answer, and it publishes the two things the down bag does not: a 24 × 30 cm (9.4 × 11.8 in) packed size and a double-layer fill construction. Its -23 °C (-9 °F) and -5 °C (23 °F) sit in the title with neither of them labeled, so the only figure you can actually read as a comfort temperature is the stated 0 °C (0 °F).
Fill power measures how much volume a given weight of down expands to fill — the loft it produces per gram. 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 (41 °F) and limit 0 °C (0 °F) stated · 20D nylon shell · 760 g (26.8 oz) / 885 g (31.2 oz)
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 (26.8 oz) and a 650 fill power down bag are the reason for the purchase.
Mummy · 350 GSM double-layer fill · comfort around 0 °C (0 °F) stated · 1900 g (67 oz) · 24 × 30 cm (9.4 × 11.8 in) packed · 230 × 82 × 55 cm (90.6 × 32.3 × 21.7 in)
A large mummy bag that names a comfort temperature of around 0 °C (0 °F), 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 (90.6 in) bag and a stated comfort figure matter more than carried weight.
Prices in these summaries were read on the dates each review gives. The live figure sits beside every product.
