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Outdoor Research Ultralight Compression Sack

rated 4.5 of 5 stars
photo: Outdoor Research Ultralight Compression Sack compression sack

Light, water resistant, and effective.


  • Extremely light
  • Very tough


  • None yet

If you're a backpacker, you'll be familiar with the difficulty of cramming everything you might need for a few days into your pack.

If you're looking to use less space, the solution is a compression sack. The sack simply squashes all the air out of anything you pack inside it so it takes up less room. The typical design includes a lightweight bag, with end caps that are connected by straps that can be cinched down. By going round and round tightening a bit at a time, you can gradually remove most of the air.

I have a couple of the OR U/L sacks in different sizes, and they are the best compression sacks I've found.

Let me put it this way; I can take a -10°C down sleeping bag and squash it down to a bundle just a bit bigger than a softball. Typically, I'll use one compression sack for my sleeping bag and a second, smaller one for all my clothes. Packing both takes up a very small part of my backpack — in fact, I could do an overnighter with a daypack instead.

The technique is simple: stuff something into the bag and do it up, position the two end caps and attach them together using the straps, then go around in a circle cinching down each of the four straps in turn until you bottom out. Result: A hard and very concentrated bundle that takes up an amazingly small amount of room.

The biggest application is to compress a sleeping bag, since they are generally one of the bulkiest items in the pack, but the bags can be used for clothing or anything else that takes up a lot of space. I've even used them as a handy stuff sack for dehydrated food, although that tends to not be very compressible.


In their ultralight line, Outdoor Research offers a wide range of sizes (8, 12, 15, 25 and 35 litres) with weights ranging from 103 to 160 grams. Made of 40-dernier silicone-impregnated ripstop nylon, they offer both compression and a degree of water protection with a very light weight. The closure uses a tough Hypalon clip, and the lid includes a built in pocket for self-storage.

OR also offers their Airpurge line, which is billed as completely waterproof, but both the price and the weights are much higher. I'd use those for kayaking, or perhaps on the wet Pacific Coast trails, but for use on the dryer Alberta side of the Rockies I'll go for the reduced weight instead.

I'm always surprised by the amount of pressure I can apply just by cinching down the straps. A down sleeping bag that might normally fit into a bag 12” wide and 18” long can be compressed into a solid package that might be only 8” by 10”. The straps and buckles on the OR bags seem to be indestructible – I will use my full strength to tighten each strap in turn, and after a number of years, I've yet to have one break or even pop free. This method lets even people with less strength get a solid, tight bundle.

The cost of the U/L line is cheap enough ($17 for the largest size) that having a few of them means I can use the right ones for each trip. I might use a medium size for my sleeping bag and a smaller one one for clothes, and if I'm looking at hanging my food off a bear pole, one of these makes a convenient package.

One good suggestion for finding the right sizes for your needs is to take your sleeping bag (or other compressible items) down to whatever store you're buying the sacks from and try them out. Watch out for ones that bottom out – you're better off to have a bit of leeway after cinching everything down rather than to have a bag that's not being compressed as much as possible.

Source: bought it new
Price Paid: Varies by size

Finally replaced my heavier Granite Gear and Alps compression sacks with this OR Ultralight and couldn't be happier!


  • Feather weight
  • Compresses well with my 10 degree down bag
  • Self storage pocket is very handy when stowing away the gear
  • Stitching seems well done


  • Not really a con yet, but curious how well it holds up after years of use
  • Sleeping bag bulges out the side some

I bought one of these for my daughter last year and really liked how much lighter it is than my older GG and Alps compression bags. When one of the online stores had it on clearance this past winter, I grabbed one for myself and I'm really glad I did. My 10-degree down bag is already heavy and this stuff sack adds barely any extra weight. Plus, the material is very slippery and makes packing/unpacking it in a tight backpack that much easier.

The material and stitching are quality and I don't foresee any issues. The straps are reinforced with double stitching and the buckles are beefy enough to not break. Plus, it's designed to pack itself in one of the lid pockets so when it comes time to store it, you don't have a spaghetti mess of straps in your camp box.


The one thing I've noticed that I don't have as much of a problem with on my GG and Alps sacks is the bulging to one side when compressing. Not too much of a big deal but it makes the load a little lopsided. 



Source: bought it new
Price Paid: $10.35

Does the job it was meant to do.


  • Lightweight
  • Does not bulge at the side
  • Comes in different sizes
  • Sturdy and long lasting
  • Stow away pouch

I purchased the OR compression sack when I got a new sleeping bag  You can see why. It packs up small and leave it in with the bag 8lt pouch


I’ve been using this one about 15x a year for about 10 years and it is showing no signs of wear. 

Works very well. I have had cheaper models that seem to bulge at the sides (what’s the point?). That is not the case with the OR.

The four straps allow you to evenly cinch down the contents to what my kids call a big jelly bean.



I also have a smaller one for compressing clothes that I will take in the B/C and in the evening it will double as a pillow.


These sack allow me to get away with a 45 Lt pack on summer excursions.

Source: bought it new
Price Paid: Long time ago

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The Ultralight Compression Sack was previously known as the Outdoor Research Helium Compression Sacks.


Price MSRP: $27.00
Historic Range: $2.00-$55.00
Reviewers Paid: $10.35
Product Details from Outdoor Research »

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