A bothy bag labelled for four people is not twice the size of one labelled for two. On one of the shelters here, it is actually narrower.

For most walking groups in Eryri the Summit Bothy Bag 4 Plus Person is the size to buy. It has the most headroom of anything on this page, at a published 1.20 m.

Every figure below is quoted from the maker’s own product page, read on 17 September 2026. We compile and explain public route and safety information. We guide nobody and sell nothing on the hill.

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Two people, and the smallest thing that works

Best where the shelter is insurance you hope never to open.

Lifesystems Ultralight Survival Shelter 2 220 g, packs to 140 x 75 x 75 mm 1400 x 900 x 450 mm up, 20D siliconised nylon, 3000 mm hydrostatic head Read the full specification on Amazon

What Lifesystems publishes for it:

• A weight of 220 g
• A packed size of 140 x 75 x 75 mm
• An unpacked size of 1400 x 900 x 450 mm
• 20D siliconised nylon with a 3000 mm hydrostatic head
• An air vent, waterproof seating panels and reflective strips

Read that unpacked height again, because it decides the whole purchase. At 450 mm this shelter is knee-high with two people under it.

That is not a sit-up shelter. It is a low canopy you get under and stay low inside.

For a pair moving fast on a long day, 220 g is the argument. It disappears into a day sack and you forget it is there.

If you want somewhere to sit out an hour of weather and eat something, this is the wrong shape for that.

Two people who want to sit up

Best for a pair who want a shelter they can actually use for a stop.

Summit Bothy Bag 2 Person 1.20 x 0.65 x 1.10 m up, packs to 11.5 cm diam by 18 cm Window, two 30 cm vents, pole loops, lifetime guarantee Read the full specification on Amazon

Summit publishes this:

• Dimensions of 1.20 m long, 0.65 m wide and 1.10 m high
• A weight of 364 gm
• A stuff bag 11.5 cm across and 18 cm long
• RPtex PU coated fabric, 4000 HS
• A window, two velcro air vents of about 30 cm, and corner loops for walking poles

The 1.10 m height is what you are paying the extra 144 g for. Two people can sit upright inside it rather than crouch.

The window is the other difference, and it is not decoration. You can see the weather without opening the shelter and losing the warmth in it.

Summit adds one caution on its own page. For extreme arctic use and high windchill it points buyers at its Supalite instead, which has no window.

Four people

Best for the common case: a walking group of three or four on a Welsh hill.

Summit Bothy Bag 4 Plus Person 1.25 x 1.10 x 1.20 m up, packs to 12 cm diam by 19 cm Most headroom on this page, window, two 30 cm vents, pole loops Read the full specification on Amazon

Summit publishes this:

• Dimensions of 1.25 m long, 1.10 m wide and 1.20 m high
• A stuff bag 12 cm across and 19 cm long
• RPtex PU coated fabric, 4000 HS
• A window, two air vents, a draw cord round the base and reflective loop tabs
• A lifetime guarantee with free repairs

Compare the width with the two person bag: 1.10 m against 0.65 m. That is where the extra capacity has gone, and it is the number that matters when four people sit down.

The height goes up as well, to 1.20 m. That is the tallest figure published for any shelter on this page.

There is one thing to know about its weight before you order, and it needs a section of its own.

Six to eight people

Best for a leader, a club group, or anyone responsible for more than their own party.

Summit Bothy Bag 6-8 Person 1.75 x 1.30 x 1.15 m up, packs to 13.5 cm diam by 21 cm RPtex PU 4000 HS, window, two 30 cm vents, pole loops Read the full specification on Amazon

Summit publishes this:

• Dimensions of 1.75 m long, 1.30 m wide and 1.15 m high
• A shelter weight of 720 gm
• A stuff bag 13.5 cm across and 21 cm long
• RPtex PU coated fabric, 4000 HS
• A window, two velcro vents, corner pole loops and a base draw cord

This is the first size where the length grows rather than the width. It goes from 1.25 m to 1.75 m, which is what lets a second row of people sit down.

The height actually drops slightly against the four person bag, from 1.20 m to 1.15 m.

At 720 gm it is no longer a thing you forget about. For one walker carrying it for a group of eight, that is the trade.

Where the labels stop agreeing

Set the published dimensions beside each other and the labels stop lining up. A person count is a name, not a measurement.

Shelter	Stated for	Length	Width	Height
Lifesystems Ultralight 2	2 people	1.40 m	0.90 m	0.45 m
Summit Bothy Bag 2	2 people	1.20 m	0.65 m	1.10 m
Summit Bothy Bag 4 Plus	4 people	1.25 m	1.10 m	1.20 m
Summit Bothy Bag 6-8	6 to 8 people	1.75 m	1.30 m	1.15 m

Two shelters on that table are both sold as two person, and they share no dimension. One is 0.90 m wide and knee high. The other is 0.65 m wide and stands over a metre.

Lifesystems takes it further than that. Its Ultralight 4 is published at 1400 x 800 x 900 mm, against 1400 x 900 x 450 mm for its Ultralight 2.

Its four person shelter is 100 mm narrower than its two person one. The same length, less width, and twice the height.

Nothing there is a fault. It is a different design decision, sold under a number that hides it.

The same length, less width, and twice the height.

Then there is the weight of the Summit 4 Plus, which is published three times and never the same way twice.

Summit’s own listing says 0.380 kg. The description further down the same page says 485 gm approx. The Amazon listing gives an item weight of 495 grams.

Three figures for one shelter, on two pages, from one maker. The 6-8 and the 2 person pages carry the same split. This is how Summit writes its pages, not a slip on one of them.

Take the higher figures as the ones to plan a rucksack around.

Walking alone, and the days you can leave it behind

A bothy bag warms the people inside it with their own heat. A four person bag with one person in it is the wrong buy.

What a solo walker wants is the one person size, not a different category. Lifesystems sells one, and says it fits one person with a daysack.

Lifesystems Survival Shelter 1 265 g, packs to 170 x 100 x 100 mm 5000 mm hydrostatic head, window, air vent, taped seams Read the full specification on Amazon

What Lifesystems publishes for it:

• A weight of 265 g
• A packed size of 170 x 100 x 100 mm
• An unpacked size of 1400 x 900 x 450 mm
• A 5000 mm hydrostatic head, with taped seams
• Waterproof seat panels, an air vent, a window and reflective strips

That 5000 mm is the highest waterproof rating on this page. The two Ultralight shelters are published at 3000 mm.

The other solo option is a bivi bag, and it is a genuinely different thing rather than a smaller version of the same idea.

You sit under a bothy bag, upright, with the fabric pulled down over you and your rucksack. You lie down inside a bivi bag, which is a waterproof outer skin for you or your sleeping bag.

One is for waiting out an hour of weather. The other is for spending a night out.

The same maker sells one, and the Lifesystems Venture Solo Bivi is what that shape looks like.

The British Mountaineering Council lists an emergency shelter in what to carry for winter hill walking. It sits there beside spare gloves, a hat and a head torch.

The Council names a bivi and a bothy bag side by side as the two answers.

Season matters more than the summit does. A shelter earns its weight on a short winter day far more than on a long June one.

If your walking is the Llanberis Path in August, in a pair, with an hour of daylight spare, you can honestly leave it at home.

How to size one for your own group

The person count tells you what the maker had in mind.

The width tells you whether your group fits.

Four adults in waterproofs, with rucksacks pulled in beside them, are sitting shoulder to shoulder. On the Summit 4 Plus they have 1.10 m of it.

Count the people who will actually be with you, then buy the size above it if the walk is a winter one. Bulky layers take room that a summer figure does not allow for.

Height is the second question and it decides comfort rather than fit. Under 0.50 m you are lying low; over 1.10 m you are sitting up.

The third question is who carries it. A shelter in the boot of the car has never helped anybody.

Which size to put in the sack

For three or four walkers, the Summit Bothy Bag 4 Plus Person is the one to own. It is the widest and tallest shelter here per person carried, and Summit publishes every dimension for it.

For a pair who want to sit out weather rather than just survive it, the Summit Bothy Bag 2 Person does that at 364 gm.

For a pair counting every gram, the Lifesystems Ultralight Survival Shelter 2 weighs 220 g and asks you to accept a 450 mm ceiling.

For anyone walking at the front of a group, the Summit Bothy Bag 6-8 Person covers the party you did not plan for.

Whichever you buy, the number on the label is where the decision starts, not where it ends.

A shelter turns a bad afternoon into a wait. The reasons a day goes wrong in these hills are worth reading first, in why walkers need rescuing in Snowdonia.