The Best Bivy Sacks: 4 Compared (and One to Skip)

RBE top pick

Rab Ridge Raider Bivi

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The Ridge Raider has the stated hoop, laminate shell and mesh door that make a bivy livable. The Storm Bivi gives up some breathability and the hoop for a lower spend.

A bivy sack is a waterproof shell for your sleeping bag, and the useful ones range from a flat cover to a hooped one-person shelter. The field splits into planned-use bivis built from breathable laminates and emergency film bags meant as a last resort. We compared two Rab bivis and an Outdoor Research bivy from current maker pages with one reflective emergency bag, and left out models listed as out of stock when we looked. Specs here come only from what each maker states.

RBE top pick

Rab

Rab Ridge Raider Bivi

Buy it

A hooped, freestanding single-skin bivi with a three-layer breathable shell and room to sit up.

Best for: Hikers and bikepackers who want rain protection and sitting room without carrying a tent.

$$$ · premium

Why we like it

• Rab states an overhead hoop at the head end plus a micro pole at the foot, so the fabric stays off your face.
• The 15D Pertex Shield Air shell is stated at 15,000 mm hydrostatic head and 20,000 g/m2/24h MVTR.
• A zipped entry with an internal mosquito mesh door, nine DAC V-stakes and three guy lines are included.

Know before buying

• At 890 g it weighs well over the Helium UL Bivy at 511 g.
• It packs to 32 x 15 cm, much bigger than a flat bivy.
• It is the most expensive way to avoid carrying a tent.

Check price on Amazon Read our detailed assessment ↓

Rab

Rab Storm Bivi

Buy it

A coated-nylon bivi with a stated spec sheet, sized for larger sleeping bags.

Best for: Buyers who want a real waterproof bivy with published numbers and a lower spend than the laminate models.

$$ · mid-range

Why we like it

• The 40D nylon top is stated at 10,000 mm hydrostatic head with a tougher 70D nylon base also stated at 10,000 mm.
• Rab says the 3D construction is meant to fit larger sleeping bags.
• It packs to 25 x 12 cm at 547 g, and the maker names bikepacking, mountaineering and multi-day treks as uses.

Know before buying

• The shell is a coated fabric stated at 10,000 g/m2/24h MVTR, half the stated figure of the Ridge Raider's laminate.
• The maker page does not say whether it has a hoop or pole.
• It is 36 g heavier than the Helium UL Bivy, which lists a pole and mesh.

Check price on Amazon Read our detailed assessment ↓

Outdoor Research

Outdoor Research Helium UL Bivy

It depends

A single-pole bivy with a 2.5-layer Pertex shell and bug mesh, light but short on published ratings.

Best for: Ultralight backpackers and climbers who want a pole and bug mesh at close to the weight of a flat bivy, and can live without published ratings.

$$$ · premium

Why we like it

• At 511 g (18.02 oz) it is the lightest planned-use bivy here, and it still lists a single DAC aluminum pole and no-see-um mesh.
• The top is 2.5-layer Pertex Shield NetPlus in 30D recycled nylon over a 40D PU-coated floor, fully seam taped.
• Outdoor Research lists dual passive ventilation flaps to reduce condensation, a clamshell opening and a high-volume toe box.

Know before buying

• The maker page states no hydrostatic head or MVTR figure, so the shell cannot be compared with the Rab numbers.
• The page lists no packed size and no length, width or head height.
• It comes with four stakes and one guy line loop, against nine stakes and three guy lines on the Ridge Raider.

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We'd skip it

Titan Survival

Titan Survival Emergency Sleeping Bag

Skip it

A reflective film bag that is fine as a backup and a weak substitute for a real bivy.

Best for: Someone building a cheap backup for a first aid or car kit, not a shelter to sleep in on purpose.

$ · budget

Why we like it

• It weighs 4.3 oz (120 g) including its stuff sack.
• It packs to 6 x 3.25 x 3.25 in, small enough for a go-bag or glovebox.
• The maker lists use as a liner, bivy cover, ground cover or distress signal, and it comes in safety orange.

Know before buying

• The page gives no test method behind its claims of retaining up to 90 percent of body heat and testing down to 40 degrees F.
• The page carries no safety warnings or limits.
• A film shell does not breathe like a laminate fabric, and the page does not address moisture build-up.
• Unrolled it measures 36 x 78 in, which the maker lists as designed for a single adult.

See our pick instead Find it on Amazon anyway Read our detailed assessment ↓

How we judged the field

Five things matter in a bivy. First is the shell: the fabric and its stated waterproof rating (hydrostatic head) and breathability rating (MVTR), because a shell that keeps rain out but traps your breath leaves you damp anyway. Second is weight and packed size, since the point of a bivy is to carry less than a tent. Third is structure: hooped designs hold fabric off your face, flat designs do not. Fourth is the stated use, so an expedition bivy is not judged as an emergency bag. Fifth is whether the maker’s page states limits. For anything safety-adjacent, a number that is not on the maker page is left out.

The field splits into planned-use bivis built from laminates or coated nylon, and reflective film bags sold for emergencies. We picked two Rab bivis because their pages state fabric, ratings, weight, packed size and dimensions, the Outdoor Research Helium UL Bivy as the light single-pole option from a different maker, and one film bag as a contrast. Terra Nova and Mountain Equipment pages did not give enough verified detail to rank.

The Ridge Raider is the one to buy if you want a bivy that behaves more like a one-person shelter than a sleeping bag cover. Rab describes it as a freestanding, single-skin bivi with an overhead hoop at the head end and a short micro pole at the foot, so the fabric stays off your face and you can sit up and get dressed. The shell is 15D Pertex Shield Air, a three-layer laminate that Rab rates at 15,000 mm hydrostatic head and 20,000 g/m2/24h MVTR, over a bathtub base with taped seams. It adds a zipped entry with an internal mosquito mesh door, nine DAC V-stakes and three guy lines. The cost is size and weight: 890 g (31.4 oz) and a 32 x 15 cm pack, well above the 511 g Helium UL Bivy. Rab states 240 cm length, 80 cm shoulder width and 60 cm head height. It suits hikers and bikepackers who want rain protection without a tent and will carry extra grams for room to breathe.

The Storm Bivi is the value pick because it keeps the useful parts of a mountain bivi and drops the premium laminate. Rab lists a 40D nylon top with a PU coating, 10,000 mm hydrostatic head and 10,000 g/m2/24h MVTR, over a tougher 70D nylon base also stated at 10,000 mm. That is a coated fabric, not a three-layer breathable laminate, so expect it to move less moisture than the Ridge Raider. Weight is 547 g (19.3 oz) and it packs to 25 x 12 cm, with a stated 230 cm length and 80 cm shoulder width. Rab says the 3D construction is meant to fit larger sleeping bags and names mountaineering, bikepacking and multi-day treks as uses. The maker page does not say whether it has a hoop or pole, so assume a flat design and plan for fabric close to your face. It is for the buyer who wants a real waterproof shell with a published spec sheet and a lower spend than the laminate models.

The Helium UL Bivy is the lightest planned-use bivy here at 511 g (18.02 oz), and unlike the Storm Bivi it lists structure: a single DAC aluminum pole, a clamshell opening and no-see-um mesh. Outdoor Research makes the top from 2.5-layer Pertex Shield NetPlus in 30D recycled nylon over a 40D PU-coated floor, fully seam taped, and adds dual passive ventilation flaps to cut condensation and a high-volume toe box. It ships with four aluminum stakes and has six stake loops and one guy line loop. The catch is the spec sheet. The page states no hydrostatic head or MVTR figure, no packed size and no length, width or head height, so you cannot set its shell or room against the Rab numbers. A 2.5-layer shell is also a different build from the three-layer laminate on the Ridge Raider. It suits ultralight backpackers and climbers who want a pole and bug mesh at close to flat-bivy weight. It is the wrong choice if you want published ratings or room to sit up through days of rain.

Titan Survival’s Emergency Sleeping Bag is a reflective film bag, a different product from the other three. It is a fair buy as a few ounces in a kit and a weak choice as a bivy you plan to sleep in. The maker page says it is an aluminized polyolefin it also calls Mylar, 35 to 40 microns thick against what it calls a 19 micron industry average. It weighs 4.3 oz (120 g) with its stuff sack and unrolls to 36 x 78 in. The page claims the bag retains up to 90 percent of body heat and was tested down to 40 degrees F, but gives no test method. It lists uses as a liner, bivy cover, ground cover, poncho and signal, and carries no safety warnings or limits. A film shell does not breathe the way the laminate bivis do, so moisture can build up inside over a night, and the page does not address that. Keep one as a backup in a first aid or car kit. Do not substitute it for the shelter and sleep system you would otherwise carry.

Rab Ridge Raider Bivi vs Rab Storm Bivi: which should you buy?

The Ridge Raider and the Storm Bivi are both planned-use bivis, and the gap is structure and shell. The Ridge Raider adds a stated hoop, a laminate rated 15,000 mm and 20,000 g/m2/24h, a mesh door and more than 300 g of extra weight. The Storm Bivi uses coated nylon rated 10,000 mm and 10,000 g/m2/24h, with no stated hoop, and it is lighter at 547 g.

Choose the Ridge Raider if you will spend real hours inside: wet weather, long nights, a need to sit up. Choose the Storm Bivi if you want a waterproof cover for mostly short or fair-weather nights and care about spend. Either way, the bivy is only the shell, so match it to the sleeping bags and sleeping pads we cover separately.

What to look for

• Stated shell fabric: a maker that names the laminate and its denier is giving you something to check. A bare word like waterproof is not a spec.
• Hydrostatic head and MVTR: the first is the stated waterproof rating in millimeters, the second is the stated breathability. Compare them within the same brand’s listings.
• Hoop or flat: a hoop gives headroom and keeps fabric off your face, while a flat design is lighter. Check that the page actually states which one you are getting.
• Weight and packed size: the numbers should be stated by the maker, in the same units you are comparing, and for the exact model.
• Stated use: an expedition bivi, a bikepacking bivi and an emergency film bag are built for different jobs. Match the stated use to yours.
• Limits on the page: for emergency gear, a maker that states temperature limits and test methods is easier to trust than one that only lists claims.

Our final take

Buy the Ridge Raider if you want a bivy that you can actually live in, and the Storm Bivi if you want a waterproof shell for less. Pick the Helium UL Bivy if low weight with a pole and bug mesh matters more to you than published waterproof ratings. Treat the Titan film bag as a backup you hope never to need, not as a shelter. A bivy does not replace a tent for long storms or a pad and bag for warmth, so budget for those first.

Deciding between the top two? See our head-to-head: Rab Ridge Raider Bivi vs Rab Storm Bivi.

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