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Your cart is empty.Sea to Summit Reactor series insulated sleeping bag liners can extend the comfort range and improve personal hygiene of any sleeping bag. Thermolite hollow core fibers are constructed like the fur of a polar bear, efficiently trapping heat and providing a luxuriously soft, comfortable feel. The stretch-knit fabric provides optimal comfort, and ensures the Reactor fits any sleeping bag. Additionally, the drawcord footbox offers plenty of ventilation and the versatility of walking around camp while still wearing your liner. Available in three different weights, Reactor technical liners make your existing sleeping bag warmer and more versatile. The Regular Liner uses hollow-core Thermolite Pro fabric with infra red-absorbing ceramic pigments and Thermolite EcoMade fibers. This lightweight fabric adds up to 14F of warmth to your sleep system. The Extreme Liner features a thicker hollow-core Thermolite Pro fabric to add up to 25F of warmth to your sleep system. The Fleece Liner employs hollow-core Thermolite Pro fibers in a grid-pattern to deliver our warmest sleeping bag liner which adds up to 32F of warmth to your sleep system.
Kevin Moate
Reviewed in the United States on February 27, 2025
Good addition to any sleep system.
Ian
Reviewed in the United Kingdom on February 26, 2025
Great item, thank you.
daveNYC
Reviewed in the United States on February 23, 2025
I used this during a recent 3 day competition where we had to carry all of our gear and camp outside. Winter storm was predicted so I got this to bolster my sleeping bag. It got down into the teens and we had 5”+ of snow one night. This definitely helped keep me warm, especially sleeping on an ultralight foam pad.Packs down small and doesn’t weigh too much for the warmth it provides.Probably way overpriced for what it is (someone with basic sewing skills could probably make this for half the price), but if you need some extra insulation that doesn’t get too much in the way of sleeping, this is a good purchase.
CpJws
Reviewed in Japan on February 18, 2025
SeaToSummitの新型ライナー3つのうち、一番温かいモデル。最初混乱したが、保温性はリアクターライナーが最低、リアクターエクストリームライナーが中間、リアクターフリースライナー（この製品）が最高ということになっている。最上位モデルにエクストリームと名付けるわけではないらしい。3つのうちで、この製品だけがThermolite®Proを使っていないので、商品説明にもこの製品だけ「身体が発する赤外線を吸収/反射する」という文言がない。ライナーで体の熱を反射しちゃったらシュラフに熱が伝わらないから結局寒いんじゃないの？という疑問は、とりあえずこの製品には関係ない。シュラフの中でジップとコードを完全に締めると非常に温かい。何なら暑い。ところが肩や腕がライナーから出るようにすると途端に寒く感じる。試しにシュラフなしでライナーだけにくるまってみると外気に触れている部分が妙に寒く、一方でマットに触れている側は妙に暑い。思うに、「内側（普通は人間の体）の熱をよく受け取る、自身の蓄熱性もそれなりに高い、外側（普通はシュラフ）にも自身の熱をよく渡す」ということではなかろうか。要するに単なるフリースだ。正直、温度調整がピーキーでかなり難しいと感じた。構造はジップやボタンなど結構複雑で、暗い中手探りで開け閉めしたり位置を整えるのが割とストレス。いっそ単なる巾着構造にしてくれと叫びたくなる。シュラフの中で微妙な寒暖に合わせて開放具合を調節・・・とかやってられない。肌触りは悪くはないが、特に良いとも思わない。身長170cmちょっとなので長さ198cmのコンパクトで十分かと思ったが少し足らなかった（なんでだ）。コンパクトでも本体のみで403gあり、それほど軽いわけではない。ほとんど圧縮できないので量的にもかさばる。手持ち寝具への温かさの追加を求めるなら、シュラフカバーか追加キルトが先で、それでも足りないと想定される時に初めてこのライナーの携行が選択肢に挙がると思う。夏のシュラフ替わりという選択肢も提示されているが、わざわざこの重くてかさばって温度調整の難しい製品である必要はないと思う。
Juju40
Reviewed in France on January 7, 2025
Parfait, très bonne qualité
Kyle Bader
Reviewed in the United States on January 3, 2025
I bought this to use as a sort of sheet over a sleeping pad for a multi day trip in the Sierras where I used a few quits instead of a typical mummy bag. Worked great for this purpose, the liner has a very nice feel to it, much better than sleeping directly on a sleeping pad.
Ricky Spanish
Reviewed in the United States on December 8, 2024
If you’re not new to the outdoors and outdoor equipment, you know Sea to Summit is a good brand. It’s a great sleeping bag liner. It adds the extra warmth I needed.
Chris
Reviewed in the United States on December 30, 2024
I've used this liner a few times in cold backpacking situations. It works well. I recommend it!
Brad K.
Reviewed in the United States on December 29, 2024
This bag liner is nice and warm. Drawstring bottom is great for sitting around the fire and keeping your legs warm. The snaps and hood helps keeps wrapped around you while you roll around at night. Was out for a cold evening and usually sleep in my puffy. Ended up taking it off in the middle of the night cause the liner was keeping me extra warm.
MASt
Reviewed in Germany on December 29, 2024
… aber von sehr guter Qualitaet! Ob die Extras im Gewebe einen Schutz vor Muffel bieten, muss sich noch zeigen! Sea to Summit bietet aber allermeist das, was sie fuer’s Geld anbieten. Die Waerme, die der “Sack” bietet ist, ist stark fuer die Dicke!
Ambra Montebelli
Reviewed in Italy on November 23, 2024
Ho utilizzato questo supporto per 7 giorni in un campo scout i primi di novembre '24 con una temperatura notturna esterna di 10°C circa ma molta umidità, zona VT. Utlizzata con sacco a pelo nuovo con temperatura comfort +5°C , tenda invernale e ben isolata. Premetto che ahimè sono una persona molto freddolosa,ma nonostante i doppi strati di intimo termico,pantaloni di pile,maglia di lana e maglia di pile la notte ho sempre avuto freddo. Il materiale si lega con gli altri tessuti per cui limita i movimenti. Pro:facile da piegare,compatto e leggero. Si lava bene in lavatrice e non stinge.Sicuramente lo userò nelle route estive al posto del sacco a pelo o sacco lenzuolo ma in inverno tutta questa differenza di comfort termico non l'ho vista. Peccato perché l'azienda ha sempre ottimi prodotti.
D Balliet
Reviewed in the United States on November 20, 2024
Did not expect to like this thing since I have restless less and claustrophobia... BUT this is a wonderful piece of gear for my cooler backpacking trips.I have a sierra cloud10 down sleeping bag comfort to 25F, but we headed out for early Nov trip in upstate NY/CT border... temps down to upper 20s so didn't want to risk it. The liner didn't tangle around my legs, nice drawstring around my head and arm holes for functional access. Nice and toasty!!! Liner also served double duty as a leg warmer/blanket while making breakfast on a cold morning.Was skeptical at first, but so glad I bought this thing. Worth the extra ounces in the backpack!!
Bekkah
Reviewed in the United States on November 11, 2024
Bought for my Virginia hike at the end of November.I wanted lighter weight and someone to keep my body heat inside.I've tested in my hammock at as low 35 degrees and has kept all cold air from flowing it!It's affordable and quality is great!Also, the pooch joins me on our nightly hammocking and he loves the warmth of it as well!
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