Rain is rarely the problem; your own moisture usually is
A bivy bag is a one-person shelter, and the specification everyone reads first is the least likely to be the problem. Hydrostatic head, published in millimetres, describes resistance to water pushing in from outside, and essentially everything on sale keeps rain out. What makes people damp is the moisture they produce themselves, so the figure to weigh against it is breathability — a moisture vapour transmission rate in grams per square metre per twenty-four hours, or a RET value — together with the test the maker names, because the scales are not interchangeable and none of them transfers cleanly to a still, cold night. Construction decides the rest. Taped seams and a waterproof zip are the difference between a rated fabric and a waterproof bag. The floor is normally a heavier denier than the top, and that number predicts how it survives being pitched on gravel. Then the shape: a flat bag packs smallest and lies against your face, while a hooped version carries a short pole over the head end, adds weight and packed bulk, and buys the space that makes a long night bearable. Check the entry — a full-length zip is easy to get into and adds a seam, a drawcord hood is lighter and slower — and read the packed size against the pack you already own. We compare fabric and denier, stated hydrostatic head, stated breathability figure and the test named, seam taping, hooped or flat construction, entry and closure type, packed size, and weight.
Emergency bag · sold as a pair · 213 × 91 cm stated · silvered inner face · no fabric, weight or packed size published
An emergency survival bag sold in twos, not a shelter bivy — it publishes a cut size and a silvered inner face, and nothing else a shelter is chosen on.
Best for: A pack or a car kit where a spare emergency bag is wanted and the specification is not the point.
≈ 15 €
Emergency bag · sold as a pair · PE film with aluminium-coated inner · 213 × 91 cm · 115 g stated · 120 dB whistle
An emergency survival bag sold in twos with a whistle sewn in — it names its film and gives a weight, and publishes nothing about breathability or closure.
Best for: A kit where a named material and a published weight are wanted from an emergency bag.
≈ 17 €
One-person bivy shelter · two aluminium poles · PU 5000 mm flysheet · sealed and double-stitched seams · 215 × 75 × 61 cm · 1.3 kg complete, stated
A poled one-person shelter sold as a bivy, publishing a flysheet water column, sealed seams and a complete-set weight — with no fabric named and no breathability figure.
Best for: A solo pitch where head room and a sealed floor matter more than packing small.
≈ 83 €
Hooped bivy · poles supplied · 3-layer laminate · 10,000 mm water column · 3,000 mvp · mosquito net · 1.4 kg and 35 × 13 × 13 cm packed, stated
The one hooped bivy here with poles in the box — it publishes a water column, a breathability number and six ground loops, and names no test for the number.
Best for: A one-person pitch where the head space of a hoop is wanted and a tent is not.
≈ 75 €
Sleeping-bag cover · Diamond Ripstop polyamide · 10,000 mm water column · 3,000 MVP · welded seams · right-hand zip · 397 g stated
The listing in this hub that publishes both numbers: a 10,000 mm water column and a 3,000 MVP breathability figure — with no test named for the second.
Best for: A sleeping bag that needs a light, fully specified waterproof cover rather than a shelter of its own.
≈ 40 €
Sleeping-bag cover · 3-layer laminate · 5,000 mm water column · breathable membrane, no figure · 225 × 85 cm · 1,300 g and 40 × 8 cm packed, stated
A generously cut laminate cover that publishes its water column, its packed size and its weight — and calls its membrane breathable without ever putting a number on it.
Best for: A cover bought for cut and closure rather than for weight, over a bulky synthetic sleeping bag.
≈ $84 / £57 / 53 €
Bivy · Pertex Shield Diamond Fuse 2.5L nylon · 30D upper, 40D TPU-laminated floor · bluesign approved · no dimensions, weight or packed size published
The only listing here to publish two deniers and name its membrane — and one that gives no dimension, no weight, no packed size and no waterproof figure.
Best for: A buyer who knows this model already and is reading the listing for its fabric specification.
≈ $170 / £188 / 200 €
Emergency bivy · 235 × 110 cm stated · one to two people · silver coating inside · 150 g and 5 × 5 × 9 cm packed, stated
A two-person emergency bivy that publishes the two figures its name rests on — 150 g and a 5 × 5 × 9 cm packed size — and names no fabric at all.
Best for: A group kit or a day pack where the smallest packed emergency shelter for two is the requirement.
≈ £23 / 21 €
Sleeping-bag cover · 3-layer Gore-Tex · polyamide face and lining, PTFE membrane · 243 cm long, 98 cm shoulder · central zip · no weight or packed size
A 3-layer Gore-Tex cover that names every layer of its construction and publishes neither a waterproof figure, a breathability figure, a weight nor a packed size.
Best for: A winter sleeping bag that needs a long, wide cover and where the membrane name is the specification being bought.
≈ 535 €
This family belongs to the sleeping out kit — see everything that has to work with it.
Prices in these summaries were read on the dates each review gives. The live figure sits beside every product.
