Long-term review: LOKSAK OPSAK || Food storage enhancer

Sunset in the Yukon Arctic. My food was stored in the clear OPSAK at the front of the shelter.

LOKSAK OPSAK bags are made of heavy-duty plastic and have a hermetic seal. When closed, the bag is airtight, waterproof, and odor-proof (the “OP” in OPSAK).

On some trips, I use the 12″ x 20″ size ($6, 1.5 oz) as a lone food sack or as a liner inside a wildlife-resistant Ursack. I also like the 9″ x 10″ size, which holds my daytime snacks and which I keep near the top of my pack.

The larger 12″ x 20″ size is ideal for storing multiple days of food. The smaller 10″ x 9″ is useful for daytime snacks, kept near the top of the pack.


LOKSAK OPSAK bags are tough, lightweight, and reasonably priced. Inside the 12” x 20” size, I can fit about five days of food. Less ravenous hikers can probably fit six.

The rectangular shape packs efficiently inside my pack, and its width fits perfectly a snack/sandwich bag, candy bar, and most energy bars. Because it is made of transparent film, the contents can be easily seen. The seal seems to blow out after 4-6 weeks, but I continue to use them for many months afterwards.

The width of the 12″ x 20″ Opsak is about the same as most candy/energy bars and snack/sandwich bags.

Recommended uses

On its own, an OPSAK is an inadequate method of overnight food protection. It’s best considered an enhancement to a more reliable method, by reducing food odors.

Most specifically, an OPSAK can be used to line an Ursack Major or Ursack Minor to make it less detectable or less interesting to a bear or rodent. Maybe that black bear two miles away won’t smell it, or maybe it’ll decide to visit a different campsite that is giving off stronger food odors.

My packed food prior to a trip in Glacier National Park, where Ursacks are allowed. My note says that I had 5 days of food in the Opsak and that it was “almost full.” I used the smaller 6″ x 9″ size for my daytime food.

If I’m using a hard-sided canister, I do not use an OPSAK as well. Canisters are not entirely bear- or idiot-proof, but I’m very confident in them as a standalone food storage method.

I never hang my food from bears, because I think other methods are more effective (e.g. canisters), or at least equally effective and easier (e.g. the Ursack Major). If you do hang your food, an OPSAK could add value to the system.

I will use an OPSAK on its own only if there is low risk (or, ideally, no risk) of bear or rodent activity at my campsites. And I will sleep with it — on it or immediately next to it, or keep it inside my shelter. I wouldn’t leave an OPSAK unattended even at “safe” campsites.

Is an OPSAK really odorproof?

Fresh out of its packaging, an OPSAK is both odor-proof and odor-free. After a few days of use, the OPSAK is probably still odor-proof (i.e. food smells do not permeate outside the bag), but I suspect its exterior becomes contaminated with food smells due to normal handling.

Bears have an extraordinary sense of smell — seven times better than that of a bloodhound, according to Yosemite — and I would imagine that this contamination puts the OPSAK on a bear’s radar. However, the food smell is probably no stronger than the food smell on your clothes or your shelter, and that level of food smell is generally not considered to reach the threshold for action. (Philmont would be a notable exception.)

To reduce food odor contamination, an OPSAK could be washed between uses with soap and water.

One 12″ x 20″ bag weighs 1.5 oz and holds about 5 days of food.


The transparent body material is heavy-duty and will withstand months of use. On my 6-month Alaska-Yukon Expedition, on which I used the OPSAK exclusively for food storage, I replaced them only twice (so two months per bag) and got several more months out of each bag on subsequent trips. Rips or tears in the body can be easily fixed with duct tape or Tenacious Tape.

The airtight seal has proven less durable, with an average lifespan of four to six weeks. After the seal blows out, I just close it up like a potato chip bag. I think this is “good enough” — if I thought that leaking food odors could make the difference, I should be using a more guaranteed food storage method anyway, e.g. hard-sided canister.

Holes in the bag body can be easily repaired with duct tape or Tenacious Tape. There is no fix for the seal, which I find blows out after about 4 to 6 weeks of daily use.

Do you have questions about or an experience with OPSAK bags? Leave a comment.

Buy now: LOKSAK OPSAK 12″ x 20″ Bag

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