thumb|Sleeping bag liner '''Sleeping bag liners''' are lightweight cloth sacks usually fitted inside sleeping bags to provide extra comfort, insulation, and help keep the sleeping bag clean.<ref>{{Cite web |url=https://www.independent.co.uk/extras/indybest/travel-outdoors/camping/best-sleeping-bag-liners-10082198.html |title=7 best sleeping bag liners to keep you warm under the stars |website=www.independent.co.uk |first=Liz |last=Dodd |date=April 22, 2019 |access-date=August 10, 2019}}</ref><ref>{{Cite web |url=https://www.dofe.org/shopping/expedition-kit/sleeping-bags-mats/ |title=Sleeping bags and mats |website=www.dofe.org |publisher=The Duke of Edinburgh's Award |access-date=August 10, 2019}}</ref>
A thin liner may feel softer against the sleeper's skin, add 5 °F warmth to the bag (not pad), and be easily washed after use (unlike the thicker sleeping bag). A thick, fleece-like liner can increase warmth by 10-15 °F. Liners also allow a sleeper to use the liner alone, without the bag in hot conditions.<ref>{{cite web |url=https://www.rei.com/learn/expert-advice/sleeping-bag-liners.html |website=www.rei.com |title=How to Choose Sleeping Bag Liners |publisher=Recreational Equipment, Inc. |access-date=August 10, 2019}}</ref> Optionally, bug-repellents, pockets, and a pillow holder can be added to liners.
A vapor barrier liner (VBL) is special type of liner that blocks the sleeper's moisture from reaching the bag, thus stopping evaporative heat loss. Usually a sleeping bag liner is used inside a VBL.
Sleeping bag liners are issued as basic kit by various militaries including the US and British armed forces.<ref>{{Cite web |url=http://www.army.mod.uk/documents/general/Black_Bag_A5_booklet.pdf |title=Clothing for Operations 'The Black Bag' |archive-url=https://web.archive.org/web/20170915194010/http://army.mod.uk/documents/general/Black_Bag_A5_booklet.pdf |archive-date=September 15, 2017 |publisher=Ministry of Defence}}</ref>
== Fabrics == {{Unreferenced section|date=August 2019}} Liners are made of silk, cotton, nylon and polyester among others; ;Silk liners: light, soft and strong and retain much thermal insulation even when wet ;Cotton: heavier and bulkier than silk and absorbs water ;Synthetic [mix]: usually light, strong, and do not absorb water
== See also == * Bivouac sack – a small, lightweight, waterproof alternative to larger tent-like shelters * Mosquito net – a type of meshed curtain that is draped over a sleeping area, to offer protection against bites and stings from pest insects, and thus against the diseases they may carry
== References == {{Commons category|Sleeping bags}} {{reflist}} {{SleepSeries2}}
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{{DEFAULTSORT:Sleeping Bag Liner}} Category:Camping equipment Category:Insulators Category:Bedding Category:Bags
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