
NEMO
Disco 15 Series
Spacious for side sleepers; bulky, temp rating optimistic.

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i would get a quilt. the aegismax wind hard quilt is great value at ~£140 on aliexpress
I would get a quilt instead of a 3 season bag; they’re lighter, more versatile and pack smaller. I have a Hyberg Slumber 400 and I love it, used it down to around 0c and kept warm. The Aegismax Wind Hard from aliexpress is amazing value if you’re on a tighter budget.
I find it much easier to regulate temperature with a quilt than a sleeping bag. If it’s cold, you can attach it to your mat with straps, but I just tuck the edges under my legs as I sleep on my back. The ability to kick a leg out and not having to faff around with zips is amazing. Mine has a closed footbox. An openable foot box doesn’t seal perfectly so often lets some cold air in. A closed footbox is also lighter. If you’re an active sleeper, definitely get a wide quilt.
I was able to push a wind hart tiny pro quilt from AliExpress down to -6 Celsius when wearing all of my layers. Might be a good option if you are open to using a quilt
In that price range I’d go with a quilt from aegis max or ice flame. Not as high quality as more expensive options but i think will offer the best bang for your buck in terms of down. I have used a kelty cosmic 20 car camping and it was not even warm to 30 degrees F (-1 C). It’s also quite heavy and bulky.
I actually quite like my aegismax. Decent enough, it frequently goes inside a 20° quilt to buy me comfort down to 0°F
I have these insanely tiny down sleeping bags from Ali Express. I typically use them as a second bag when cold weather camping but have used them when staying at airbnb etc.
I have one of these. Last time I used it was 20c at night. Ended up not using it and using a thin blanket instead. Granted its not that hot very often but was way too sweaty.

NEMO
Disco 15 Series
Spacious for side sleepers; bulky, temp rating optimistic.
Hammock Gear
Classic Burrow 20°F
Budget king; very warm but heavier than ultralight.

NEMO
Disco 30
Spoon shape for side sleepers; prone to zipper issues.

Western Mountaineering
VersaLite
Durable, very warm; premium price, too hot in summer.

Katabatic Gear
Alsek 22°F Quilt
Versatile 3-season quilt; secure pad attachment, high price.

Ranked #1
NEMO - Disco 15 Series

Ranked #1
Kelty - Tru.Comfort Doublewide 20
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Enlightened Equipment - Revelation APEX

Ranked #1
NEMO - Disco 15 Series

Ranked #1
Feathered Friends - Egret UL 20/30

Ranked #1
NEMO - Disco 15 Series