Quick Overview

Ultralight three season down sleeping bag.

Impressively light, surprisingly compact and exceptionally warm, the Helium 450 features 800+ loft down, ultralight nylon fabrics and Mont's award winning Radial Arc Baffle System. The ultimate bushwalking bag for virtually all Victorian conditions.


  • Ultralight 26 gsm nylon outer fabric
  • Radial Arc Baffle System
  • Differential cut
  • Duck down 800+ loft
  • 3D draught tube
  • Minimum Comfort Temperature -7°C

Tech Specs


3 season bushwalking


Tapered rectangular

Fill weight

450 g

Fill type/loft

Duck down 800+ loft

Shell Fabric

10 by 10 denier, 520 thread count, ultralight Nylon (26g/m2)

Inner Fabric

15 denier down proof Nylon

EN13537 Comfort Temperature


EN13537 Lower Limit Temp


EN13537 Extreme Temperature


Max User Height

185 cm

Total weight

800 g

Extra Info

Stuff sacks

Ultralight sil-nylon stuff sack, large storage bag also included


Tuck stitched, radial arc, box wall


Full length + foot



Excellent - Hard to Fault 
Review by OutdoorsmanProduct Review (submitted on 22 June 2012):
Was looking for a bag that was lighter than my vintage One Planet Bushlite. Superb bag but at 1.4Kg for a -5ºC bag looking to shave some weight. These J&H bags (bought out by One Planet) had the best loft of any bag around – including ones that were better on paper. “Guaranteed 550 loft” it was probably much better. That bag is still going strong, and having always been stored well still lofts a treat. IMHO the key to a great bag is the loft in the down. Warmth, weight, bulk all come down to quality of the down. Well the down in these Mont Helium bags is superb. 800 loft Goosedown gives superb loft and insulation and featherlight weight. The cover material feels more like silk than nylon and is not unpleasant against the skin, and again, super light, yet feels strong and supple. The lightness assists additional loft.

I did have some concern when I first unpacked the Helium 450 and left it to loft for a couple of days. A couple of the panels lofted very poorly and on closer inspection seemed to have very little down in them. Then I noticed that the underside of the same panel was thick with down. Turns out that these bags don’t have a side baffle so down can migrate from the top where you usually want it to the bottom. Undid the bag and shook the down from the base to the top and wow, what a difference. It’s bubbled up like some large Antarctic slug! It’s an advantage actually to be able to regulate the temperature in this way – you just have to know that you can!

I’m a big guy, 187cm and 110Kg and don’t like feeling claustrophobic in a bag – so like a bit of space at the foot end as well as around the shoulders. The Helium bags suggest a maximum height of 185, I’m a couple of centimetres over that and found the bag comfortably long enough – and longer than others on the market. I also found the space around the shoulders to be adequate, and again better than others on the market. For additional comfort I’m going to purchase the Mont Wedgie for trips where weight is not an issue, as this zips into the bags zipper and adds additional circumference.

The bag doesn’t have a Velcro tab on the top of the zip to prevent it opening unintentionally, and I thought that this might be a problem. It isn’t. Something to do with the design or quality of the zip, which is quite fine toothed, means that it doesn’t seem to come undone. Similarly I was concerned that he bag didn't have the rigid tape along the inside of the zip that my old bags have, to stop the zipper catching the fabric and jamming. Doesn't seem to be a problem, again perhaps because of the fine toothed zip? The bag also does not have a chest baffle, and again I thought that this might prove a problem, but again, it doesn’t. While the chest baffle seems a good idea on paper it rarely seems to work as well in practice – perhaps partly because it’s one more layer of “locking yourself into a bag” that I don’t like, and consequently don’t do it up tightly. Instead of a chest baffle, the Helium has a baffle around the opening, beyond the draw cord, which settles down around your body regardless of how tightly you have the opening draw cord cinched up. In practice this seems to work better than a chest baffle. The foot opening (“oven door”) is great and works well. I really like the way that the foot of this bag is shaped – you get the benefits of a box foot in a semi-rectangular bag. Unlike most bags the Helium has a second complete zip around the foot. Not quite sure why they didn’t just continue the zip around as in most other bags. Perhaps this is why the foot stands up in such a good shape? It does give you the option of keeping your toes toasty by opening the bottom part of the side of the bag without opening the foot – or vice versa. The foot zip opens from the side-zip side rather than what would be the “end” of the zip in a one zip bag. The second zip is cunningly designed so that you can still open out the bag completely by undoing both zips. A nice touch is that the zip baffle goes all the way around all of the zip – some bags just stop at the bottom corner. The baffle is adequate and well filled. Personally I think they could have made it a fraction larger even if it contained no more fill than at present – but I guess this could increase the risk of it catching in the zip. The fine teeth on the zip may also reduce the need for a larger baffle – will monitor this.

The hood also has a baffle around it, and is also really well shaped. It is the best and most effective hood I have ever used. Many hoods seem to have inadequate volume for one’s head, or the draw cord tightens uncomfortably across your forehead. This one just works. A minor gripe is that as with just about all bags the draw cord winds up being up above your ear somewhere, where you can’t get your hands and certainly can’t see once you’re tucked up in the bag. Not so much a problem with the hood, but when you want to get your hands out to more easily undo the zip, it’s a pain. Same goes for the zip end if you want to undo the zip. High time bag designers solved this one! One thing they could try is separating the toggles for hood and chest and placing the chest one front and centre? On this bag they are on one toggle on the opposite side from the zip, so you can open the zip without disturbing your settings.

I started by buying the Helium 450 as I thought it was rated for lower temperatures than it actually is, and so then went back and bought the Helium 600 which is comfort rated to -7ºC. The first use was camping out in -3 ºC and it was plenty warm enough, with some in reserve so I think this is an accurate (T Limit male comfort) rating. This still saves around 25-30% or 0.4Kg over my Bushlite and is rated for lower temperatures. The Helium 450 covers places I go in the mountains that can get down to -2 ºC for a couple of nights even in mid summer. Rationalising that it’s only equivalent to a few nights in a hotel, I’ve since been back to buy the Helium 300. At only 695g and a +3ºC T limit temperature rating it is exceptionally light and covers many 3 season bushwalking situations. So call me crazy, I now own all three Helium bags. The steps in temperature rating are achieved at half the weight of carrying a thermal sleeping bag liner, and at this point in my life the weight reduction is worth the extravagance!


Standard/Free shipping to major capitals takes 2-5 business days (after dispatch), with occasional delays.

Order before 11am - we usually ship the same business day!

Choose Express Post for priority packing and faster shipping.