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Keep your ascent ultralight.

The ultralight Rab Ascent 900 Sleeping Bag boasts an incredible warmth-to-weight ratio and protective features for ultralight backpackers and campers alike. Rab's proprietary Hydrophobic treatment protects the 650-fill duck down from moisture to keep you warm through rainy nights, and the windproof Pertex Microlight shell is surprisingly durable for how light it is. The bag's semi-rectangular shape is roomier than standard mummy bags, and an angled footbox offers extra room so your feet don't feel squished. The Ascent also features an internal collar and a drawcord at the hood to seal out any cold drafts, and a zippered stash pocket that's perfect for headlamps. It comes with a full-length zipper on either the right or left side, and a compression stuff sack for backpacking and a cotton storage sack to keep the bag prime for years.

  • 0° F temperature rating
  • 650-fill duck down with Hydrophobic treatment
  • Semi-rectangular shape, angled footbox
  • Pertex Microlight fabric
  • Internal collar and drawcord for hood
  • Left or right sided zippers available
  • 3 pounds, six ounces: ultralight
  • Internal zippered stash pocket
  • Compression stuff and cotton storage sacks included

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Here's what others have to say...


Warm, lightweight and packs small

  • Familiarity:I've used it once or twice and have initial impressions

I haven't had a chance to use this bag in the environments it's really built for, but have used it on for a few nights camping in CO at 13,000 feet where the overnight temps dropped to about 30 degrees. The bag was plenty warm and I left the drawcord a bit loose so as to not get too warm. It's a bit roomier than other mummy bags, but the insulating value doesn't seem to suffer from the extra air space inside. Looking forward to using it over the winter in Yellowstone and the high Uintas.


Great bag

  • Familiarity:I've used it once or twice and have initial impressions

Although I haven't used my Rab sleeping bag in extreme cold conditions yet, I can say that it looks to be a great bag, it's light, has a great fit and is really wide and spacious, useful for big and tall people.
As cons I can mention the non reversible zipper

Rab Hydrophobic Down

In the early days, Rab Carrington built his brand around down insulation, and we still see down manufacturing as a core part of the Rab brand today.

All of our down insulated products are filled with the highest quality Hydrophobic Down, developed in conjunction with Nikwax. The hydrophobic treatment is applied at source and is seen as the next step in our progression in down manufacturing.


Pretty Cool Bag...

  • Familiarity:I've used it several times

I love the fit and that it cinches around my head, creating a pocket for me to use clothes for a pillow. Nice feature. I bought the bag for a winter backpacking trip to the sierras and while it only got down to about 15-25 degrees, with snow pack, I needed to use a silk liner and a wool base layer to make sure I stayed completely warm.

Does anyone have the measurements of this bag when compressed all the way down? (down... ha) Would this bag be sufficient for an AT thru-hike starting in January as far as storage and compression capabilities? This is all around the lightest high quality 0 degree down bag I have found for under $300, but I just need details on its size when packed down. ha.... down.

Benjaminja, when the bag is compressed is like a soccer ball.. it is probably 13 o 14 inches diameter.

Benjaminja, when the bag is compressed is like a soccer ball.. it is probably 13 o 14 inches diameter.


Keeps me warm

  • Familiarity:I've put it through the wringer

Great shape, it's a little wider than normal in the foot area, which is great for putting boot liners or clothes in there with you. This bag is just wide enough for me to pull my knees up when changing pants or whatever, a nice bonus!

As far as warmth goes, the coldest I've got is probably around -15-20C and no problems with keeping warm. Compared to my wife's REI sleeping bag, my RAB feels stronger and repels water better, doesn't leak feathers nearly as bad (I've just started seeing a few sneak out), packs down just as small, and keeps me warmer. Highly recommended

Oh and the stuff sack that comes with it is way too big... I can compress it down a lot smaller with a smaller stuff sack.


Yellowstone tested.

  • Familiarity:I've put it through the wringer

I bought this for winters in Yellowstone. So far I have used it on 3 extended hikes (we had snow and blowing at 10000 ft in May) and 2 bike packing weekends.

The bag performed great in the cold (15') and was a bit too much for the summer even at 8000 ft. Slept on the pad and just had the bag draped over me.

I have read that the zippers have issues and I have not had any. I have also had someone borrow the bag for a back country trip and she had no issues and was comfortably warm while sleeping.

I am going to use this bag for a 3 week bike tour from Bozeman Montana to Tucson AZ in November so I will follow up after that.


I hate the zipper--but warm at 35F

  • Familiarity:I've used it once or twice and have initial impressions

I bought the zero degree bag as I always get cold when camping. I used it last weekend for the Ragnar Trail relay. The temps in Snowmass went down to around 35, i had an insulated thermal pad beneath me and i was only just comfortable. I also had to wear my down full-length coat inside the sleeping bag to be cozy. Thus, I don't think I'd ever attempt to sleep in this bag in sub freezing weather. The zipper is also TERRIBLE. I found myself fighting with it throughout the night to get it up all the way. Hard to grab and difficult to slide up (kept getting caught). On scale of 1 to 5 I'd give it a 3.

Hi Emily,

That's a bummer this bag didn't work out for you. I've had similar experiences with zippers and poorly filled bags in the past, so I know what it's like to buy something that you're relying on to keep you warm and it doesn't. Have you checked out the Sea-To-Summit Talus TsIII? It's a "1" degree bag aka a 0 degree. I have it's little brother the TsII 14 degree and it's very good for the price. The zipper have a light piece of rigid nylon on the baffle so it doesn't get caught every 5 inches while zipping up. It also has 750 fill duck down that's water resistant. I really like my TsII, thought I'd you give a heads up. If you are feeling rich and never want to fight with zippers again I would look at Western Mountaineering sleeping bags. They are hand made in the US and have +850 goose down fill and are generally the most comfortable bag to sleep in. I have 1 already and i'm looking at getting another.... and maybe another after that. Those are just my thoughts, good luck and stay warm!

Which circle shoulders this sleeping bag

Which circle shoulders this sleeping bag

Best Answer

Hey Pavloar,

The measurement we have listed for circumference is actually across the chest. The full girth at the shoulders should actually be 59 inches around.