This is a technically accomplished bit of kit – and with the price tag that goes with it.
Ultralight backpackers will love the startlingly low weight of just 490g.
It stuffs down to an amazingly compact 29 x 13cm – pictured below – thought it does put up a fight as you squish it in the stuff sack.
Despite the low volume, the high-quality down is strikingly warm, thanks to the 850 fill power. That said, the bag has a comfort rating of 4C – not as toasty the (800g) Therm-A-Rest Parsec -6 (see ‘also consider’, below), so be prepared to layer up before you hit the sack on a chilly night.
The drive to save weight is evident in the fabric, which is so fine that you can see the down through it; the exterior is 10-denier, the lining just 5-denier; but it seems robust enough.
Other weight-saving measures are less functional. The shape is generous enough around the upper body (depending on your build, of course) but tapers to a rather narrow fit around the legs, which I didn’t mind, but some might feel confined by the lack of wriggle room below the hips. The designers save a few more grams with a half-zip, which goes down only to the waist. This means that if you overheat, you can ventilate your top half, but there’s not much you can do about hot legs, other than remove them completely from the bag.
The premium goose down fill is rated 850 loft – the warmest available for its weight. It is RDS certified, which offers reassurance that it has been harvested humanely. The down is treated with a moisture-repellent chemical, ULTRA-DRY Down, which helps the down retain its loft and keep insulating, even in damp conditions.
On cold nights, there’s no cinch or baffle for the shoulders, but you can cinch the large hood for a close fit around the face.
The result is a bag that is wonderfully light and warm – perfect in the right conditions, but lacks a wee bit of versatility.
For more expert sleeping bag reviews head across to our list of the best sleeping bags.
Facts at a glance:
- RRP: £350
- Weight: 490 g (reg)
- Comfort: 4C
- Fill: ULTRA-DRY Down – 90/10 Premium Goose Down, 850 Loft; RDS-certified
- Fabric: 10-denier nylon
Also consider...
Thermarest Parsec -6 sleeping bag
For colder nights, the Parsec -6 is gorgeously comfortable and cosy, but at only 800g still very light. Like the Spark SpII, it packs down very small at 18 cm x 24 cm, leaving you some vital space in your pack. The generous hood is big enough for a small inflatable pillow, and optional straps attach you to your sleeping mat, so you won’t roll off in the night.
