The Sierra Designs Nitro 0°strikes a successful balance between warmth, weight, versatility and price. At 1.25kg, and packable down to a very small size, it’s a lightweight bag for winter backpacking. Weight is kept low by thin 15d ripstop nylon, a half-length zip, and minimal features. The insulation is 800 fillpower, responsibly sourced hydrophobic down. I found this  performed impressively in damp conditions. The hood is warm, easily adjusted, and closes down to very small opening. Given that I am a cold-sleeper, I found this to be a warm bag.

Rating: 4.5/5 | Price: £324.99 | Weight: 1.25kg (Size regular) | Fill: 736g 800 FP hydrophobic duck DriDown. | Shell: 15d ripstop nylon. | Zip: 2 way, half length. | Length: 198cm | Rating: Comfort -9°c | Sizes: Regular/Long | Women’s version: Yes

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I had no problems with ‘cold spots’ being caused by the down compressing or bunching up, which I appreciated as someone who switches sides repeatedly in their sleep. There is a draft tube along the length of the zip which effectively stops cold air leaking in, and a generous draft collar which wraps around your upper chest. You aren’t able to tighten the draft collar but in this case, it didn’t impact its effectiveness.

The self-sealing foot vent is highly innovative. This takes the form of a slot opening on the bottom of the bag, with no zips or Velcro to close it shut. Instead, there is a large overlap in the fabric, which creates a seal when you are lying in the bag. You can easily slide your feet out of the bag by simply bending your knees. Initially I was dubious, expecting the vent to let in cold air. However, this didn’t happen to me at all. The seal created by the overlap seemed to work perfectly. I love this feature. It extends the temperature range in which you can use the bag comfortably and provides easy ventilation without having to fiddle with zips in the middle of the night.

Overall, the Sierra Designs Nitro 0° is a very impressive sleeping bag which is well-suited to winter backpacking in the UK, and its great value too