Rab Neutrino 400 sleeping bag review

When light is right, but warmth is required, the Rab Neutrino 400 strikes a fantastic choice. Here's our review

T3 Platinum Award
Rab Neutrino 400 Sleeping Bag
(Image credit: Mark Mayne)
T3 Verdict

The Rab Neutrino 400 Sleeping Bag is the result of decades of testing and tweaking, and the 2022 iteration really showcases the results. This is a warm but light sleeping bag, and can only be criticised if you're looking for a completely different product, like a heavy synthetic sleeping bag. Recycled materials and impeccable build quality round out a very compelling product.

Reasons to buy
  • +

    Warm enough for most scenarios

  • +

    Light and packable enough to carry

  • +

    Nice design touches

  • +

    Recycled materials

Reasons to avoid
  • -

    Down doesn't like damp

Why you can trust T3 Our expert reviewers spend hours testing and comparing products and services so you can choose the best for you. Find out more about how we test.

The phrase 'Rab Neutrino' will be burned into many an outdoor-person's consciousness. This brand has built an industry-leading reputation in down jackets and makes what are generally considered the best lightweight sleeping bags around (as well as, some of the best sleeping bags in general). 

The newly uprated spring/summer 2022 Neutrino collection ranges from the Neutrino 900, which is rated down to minus 22C, to the Neutrino 200, at minus one. For this particular review, I tested the middle option, the Rab Neutrino 400 (20F) down sleeping bag. 

With a temperature limit of -7C / 20F, the 400 is designed to offer a balance of warmth and light weight, intended for mountaineers, alpinists, and anyone who wants a light bag that'll keep them warm. It's available in men's and women's versions, as well as wide, long, and long + wide variants, with prices starting from £360 / US$400. Here's my full Rab Neutrino 400 Sleeping Bag review. 

Rab Neutrino 400 Sleeping Bag review: design and build 

Rab Neutrino 400 (regular) specs

Weight: 775g / 27oz
Temperature rating: 
-7C / 20F (limit)
800FP European Goose Down
20D Recycled Nylon (38gsm)
Pack size:
35 x 23cm / 13.8 x 9.1"

The important things first – the Rab Neutrino 400 Sleeping Bag weighs in at 775g / 27oz, putting it into a low-midweight category. It's comfort rated to minus one, with an 'edge of comfort' at -7C (20F).

This makes it an ideal bag for year-round use, as well as a light one. The lightness is no accident, being stuffed with 800 Fill Power Responsible Down Standard (RDS) Certified Goose Down. The down is also treated with Nikwax fluorocarbon-free hydrophobic finish, making it more water-resistant than standard Goose down, a very useful feature in the mountains (and in any damp conditions). It’s also hand-filled in Derbyshire UK, which is a nice touch and a connection to the brand’s roots. 

The outer is 20D Pertex Quantum 100% recycled nylon ripstop (38gsm) with fluorocarbon-free DWR, while the lining is 20D Recycled Nylon (38gsm), a combination of materials that feels lightweight, but not flimsy. The use of recycled materials is a welcome step, but not a move that appears to have impacted quality at all.

Rab Neutrino 400 Sleeping Bag

(Image credit: Mark Mayne)

Rab has made a variety of design choices to cut weight, including the chevron baffle design which the company has used on other ultralight sleeping bags recently. The chevron design also reduces down migration (preventing annoying cold spots) and optimises core warmth, the former also aided by the box wall construction with differential cut.  

Rab Neutrino 400 Sleeping Bag

(Image credit: Mark Mayne)

Elsewhere the neck baffle helps trap heat on colder nights, while the bungee around the head hood area allows for cinching down to help combat heat loss. In a similar vein, a 3/4 length zip helps keep the warm inside where you want it, although frankly we’d spend a few grams for the flexibility of a full zip in warmer weather, given the option.  

Rab Neutrino 400 Sleeping Bag

(Image credit: Mark Mayne)

Rab Neutrino 400 Sleeping Bag Review: comfort and performance 

A bag like this is always a fine balance between weight and performance, and Rab has struck a good note here. Performance (as you’d expect from the materials and build), is good, with plenty of warmth on offer even on chillier spring evenings. Pack size and weight make this absolutely great for the target market, but bike packers, alpine hikers and overnight adventurers of all stripes will be interested in this combination, especially in the cooler months or at higher elevations, where the ultralight summer bags really run out of steam.  

Rab Neutrino 400 Sleeping Bag

(Image credit: Mark Mayne)

The detailing is a key part of the offering here, the small phone or battery pocket being neat, unfussy and the right size not to lose small items in it. The YKK Anti-snag zip insert works surprisingly well, spreading the two parts wide to prevent the lining snagging in the teeth, and should be standard fitment on all sleeping bags from now on.  

The 800FP down lofts very well, even after being compressed, and adds to a feeling of luxury, which is rare in a bag this light. That comfort is also down to the hood and neck baffle, which work well – and indeed are both proven ‘in the field’. In testing, the down coating seemed to perform well, although it’s worth bearing in mind that down and water are still mortal enemies (head to our down vs synthetic sleeping bag explainer for more on that). If you’re planning a long, wet autumn ramble, then the Rab Neutrino 400 Sleeping Bag will need careful handling to keep it dry. Helpfully, Rab includes a waterproof roll-top compression sack for this purpose, so you don't need to provide your own dry bag.  

Rab Neutrino 400 Sleeping Bag

(Image credit: Mark Mayne)

Rab Neutrino 400 Sleeping Bag Review: verdict 

Having owned several Rab Neutrino jackets and sleeping bags over the years, it’s clear that Rab hasn’t messed with a successful formula, and indeed has improved on the older Neutrinos in several areas. 

Most importantly though, anyone picking the Rab Neutrino 400 Sleeping Bag up in 2022 is going to get exactly what they'd expect: a lightweight down sleeping bag that'll work through the seasons, and in pretty much any situation, from hillwalking to bikepacking, family camping to alpine climbing. The only possible criticism is that some bags are potentially more hardwearing (and thus heavier), and down doesn't like getting wet, so some care is required if you're using this in soggy conditions. In short, it’s as close to a real jack-of-all-trades as you can get, and certainly if lightness and packability are important.  

Mark Mayne

Mark Mayne has been covering tech, gadgets and outdoor innovation for longer than he can remember. A keen climber, mountaineer and scuba diver, he is also a dedicated weather enthusiast and flapjack consumption expert.