Compressibility
The Rab Neutrino Endurance 600 compressed with slightly more than average effort and not as compactly as some of the other bags in this category. This is likely because, as one of the warmer bags in the category, it uses 600 grams of down and a robust shell.

Warmth
The Rab Neutrino Endurance 600 is equipped with 800 down fill and has a Pertex Quantum lining that is light enough to allow the down to loft well and hold the maximum amount of heat inside the bag. I found this to be key to the bag’s warmth while also keeping weight down to just over two pounds. This bag has an extremely generous draft tube and neck baffle that helped eliminate drafts and cold spots. As someone who is a bit of a colder sleeper, I found this bag comfortable into the mid 20’s. 

Features
The Pertex Endurance outer fabric was very durable and handled condensation, weather and dirt well. Since this is the same outer shell fabric that Rab uses on their jackets, it is well suited to handle the elements, making this bag perfect for alpine climbing, winter backpacking and bivy ledges. Rab also uses a fluorocarbon free hydrophobic down in this bag to prevent any allergy issues. 

The Neutrino Endurance 600 uses a tapered shape as opposed to the traditional mummy shape, as well as an angled foot box. This shape contributed to warmth and functionality and little dead space. The anti-snag zipper webbing tape performed pretty well, but would have been even better if the tape was stiffer. The inside zippered pocket is suitable for small items such as a headlamp or very small camera, but a bigger pocket would have made it more functional. 

Overall Comfort
The Rab Neutrino Endurance 600 is packed with 600 grams of 800 fill down making this bag comfortable and warm and made me feel like I was surrounded by pillows. Even though the shell is tough and durable, it did not take away from the comfortable feel of the bag. The hood cinches well around your head and adds to the overall comfort of the bag.  

Durability
The Neutrino Endurance 600 performed very well in terms of durability and showed no marks or defects during the testing phase. The robust outer shell handled condensation, dirt and weather extremely well.