Weight 640g
Down Fill Weight 300g
Down 800+ loft white down
EN Temperature Rating Women's Comfort 4ºC, Men's Limit -1ºC, Extreme -17ºC
Maximum User Height 185cm
Maximum Shoulder Circumference 160cm


The Mont Helium 300 is a fantastic, lightweight, three-season…

Rating: rated 4.5 of 5 stars
Source: bought via a "pro deal"
Price Paid: approx. $350 (40% discount)


The Mont Helium 300 is a fantastic, lightweight, three-season bag. It's very compressible and light for such a warm bag. This bag has a full hood and with good layering you can take this into a mild winter's night, and contains 300g of 800+ loft white down.


  • Lightweight (658g w/ stuff sack)
  • DWR down
  • Foot vent
  • Full-length zipper


  • Not the lightest in class, but close
  • Zipper snags

The Mont Helium 300 is my three-season bag for wilderness guiding in Tasmania. I am typically a warm sleeper, but with the temperature swings we are prone to here on the island, it is good to have a versatile sleeping bag.

I own a number of Mont products (which will be reviewed as time passes) and I have noticed a great attention to detail in regards to the target use of the item. I have used this bag for a season consisting of almost 100-nights in the bag. It has lasted well, and has no signs of wear except that it kinda smells like I've been sleeping in it too long :)

The website lists the construction as: "Durable 10 by 10 denier, 520 thread count Nylon weighing only 26g/m2 with a hot-rolled-cire treatment to prevent down leakage and increase durability." I have not noticed any down leakage at this point and the materials are holding up well to my use.

This bag has 300g of 800+loft down filling.


Mont has a few features that they use in most of their sleeping bags:

  • Radial Arc Baffle System
  • Differential Cut
  • Foot-box Vent
  • Hydrophobic Thread

All these are nice touches that go towards making this bag more versatile than others at its weight.

This is a reasonably warm bag. The women's comfort rating is 4°C and the men's is -1°C. I have been comfortable in the single digits with a silk liner, but that is as far as I would want to take it without full sleeping thermals. Having the full hood allows you to get a lot more warmth out of the bag by cinching it tight.

On the other hand, during the summer I leave the foot-box zip open to regulate my temperature.

Fit and Comfort:
I am 175cm tall and 70kg and this bag fits well and has enough length for a pair of clothes in the foot-box. It is not too tight nor too roomy. The hood has room for a small pillow or stuff sack full of clothes. The Mont sleeping bags have a nice roomy foot-box that fits my size 11 feet easily. This is a light and lofty bag that has a nice soft texture.

Entry and Exit:
This is my first left-hand zip bag, and that took a little while to adapt to. The main zipper runs the length of the bag and there is a secondary zipper just for the foot-fox. It is easy to get in and out of the bag, or to just use is as a top blanket. The only gripe I have is that the zipper snags easily, but this is probably due to the lighter fabric and reduced zip-tape stiffness.

The down is DWR treated, and the threads used for stitching are hydrophobic. I have had no issues with moisture as it all seems to pass out of the bag.

I originally bought this bag due to its packability. When compressed into the supplied silnylon sack, it is hardly bigger than a Nalgene bottle. The compressed size of the bag is around 16cm x 20cm

The advertised loft is "800+ white down" with each down batch being individually tested. My bag was tested as 835-loft. The down is very lofty and puffs up quickly when unpacked. There is a much larger amount of down in the top of the bag than bottom.

Ease of Use:
All features are simple and easy to use. Nothing crazy here.

This bag has been used in lodges and camp scenarios ranging from a cold, wet, 3-degrees Celsius to the mid-20s and dry. It has had about 100 nights of use over a guiding season (approx. 6 months), including personal camping trips.



I have used this product through a season of wilderness guiding in Tasmania. I have owned it for about nine months and used it for just over six months before switching to a winter sleeping bag. It has covered almost 1000km and 100 nights of three-season use. The climate has been mostly coastal, with some mountain use.

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