Pajak Core 400 Review

Overview

The Core 400 is the workhorse of Polish down specialist Pajak’s range: a 700-fill duck down mummy bag for spring-to-autumn trekking, rated to 0°C comfort. It weighs 800 g in the Regular length and costs roughly €290–325 at European retailers. The trade-off is plain: it isn’t the lightest bag at its temperature rating, but it undercuts most of the competition on price and gives back some of that weight as room to move.

Key Specs

Spec	Value
Weight	800 g (Regular)
Fill	700 fill power Polish duck down, RDS-certified
Fill weight	422 g
Comfort temperature	0°C
Limit temperature (EN 13537)	-6°C
Extreme temperature	-24°C
Shell fabric	Duralight Shell (Toray Airtastic SLF15 with DWR, per retailer listings)
Construction	Z-shaped baffles
Closure	Double 2-way zipper with anti-cold flap
Packed volume	About 5 L (Regular)
Footbox width	50 cm
Max user height	180 cm (Regular)
Extras	3D draft collar, drawcord hood, zippered inside pocket, internal and external loops, compression sack

Performance

Warmth. The Core 400’s headline numbers are 0°C comfort, -6°C limit and a -24°C extreme figure that belongs on the spec sheet and nowhere near a night out. Owners put the real range closer to the limit than the comfort number. One long-distance hiker in the Alps reported sleeping comfortably at around -5°C, and suggested the bag could go lower. That fits the construction: the Z-shaped baffles angle the walls between down chambers rather than stacking them in a conventional H pattern, which Pajak says improves insulation. A 3D draft collar and a flap behind the zipper address the usual leaks at the neck and along the zip line.

Weight and packability. At 800 g with 422 g of fill, the Core 400 is competitive for a bag rated to 0°C, but it isn’t in the cottage-industry weight class. The 700 fill power is a step below the 800–900 fill that dominates premium ultralight bags, and that costs a few hundred grams of weight or a little packed volume. In its compression sack the Regular packs to about 5 L, around 29 x 18 cm. The sack offers two compression levels, and one owner noted that cinching it fully makes for a tight squeeze.

Breathability and range. Owners mention the bag doesn’t turn clammy when temperatures rise. The same Alps hiker used it at +10°C without trouble, and the full-length zipper lets it open out into a blanket on warm nights. The two-way zip also means a foot vent is easy to create when the hut is stuffier than expected.

Fit and comfort. This is a roomy mummy by modern ultralight standards. Reviewers on retail sites return to the same words: roomy, easily compressed, adjustable hood. Side sleepers and restless sleepers benefit. Thru-hikers chasing the narrowest, lightest cut will see that room as extra fabric and extra air to heat. The shell is soft, though one owner said it has a slightly plastic hand, which takes getting used to.

Moisture and durability. The hood and footbox carry a water-repellent DWR treatment, which is useful where condensation from a tent wall or a damp breath collects. The down is treated as standard, not hydrophobic, so it still needs a dry bag in sustained rain. Owners describe the bag as durable and well finished, and the down is traceable via a QR code on the product. It’s made in Europe.

Pros & Cons

Pros

• 800 g for a 0°C comfort rating, with 422 g of down
• Real-world use reported at around -5°C, consistent with the -6°C limit
• Breathable across a wide range, from near-freezing to about +10°C
• Roomy cut, full-length 2-way zipper, 3D draft collar and anti-cold flap
• RDS-certified Polish down with QR traceability
• Priced well below most European and North American down bags of similar rating

Cons

• 700 fill power means more weight and bulk than 800–900 fill bags
• Roomy cut is less thermally efficient than a snug ultralight mummy
• Full compression in the stuff sack is tight
• Shell has a slightly synthetic feel
• Standard (non-hydrophobic) down needs careful moisture management

Who Should Buy This

The Core 400 suits three-season trekkers, alpine hut-to-hut hikers and weekend backpackers who want a warm bag at a fair price and don’t need to shave the last 150 g. It also suits anyone who sleeps badly in a tight mummy. Thru-hikers on a strict ultralight base-weight budget, or anyone planning regular nights well below -5°C, should look at a higher-fill-power bag or a warmer model. It comes in Short, Regular and Long lengths, with the Regular covering users up to 180 cm.

Verdict

The Core 400 delivers honest 0°C-to-slightly-below warmth, a comfortable cut and sensible details at a price that makes premium down bags look inflated. It gives up some weight and packed size to 800-fill competitors, and that rules it out for gram-counters. For most three-season hikers, it’s the better value.