(as of Jun 10, 2025 04:10:04 UTC – Details)
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Sea to Summit
Reactor Sleeping Bag Liner
Thermal boost liner retains heat, adds warmth to your sleep system in colder conditions, and acts as a hygienic layer to extend the life of your sleeping bag.
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Customer Reviews
4.6 out of 5 stars 118
4.4 out of 5 stars 57
4.4 out of 5 stars 345
4.7 out of 5 stars 26
4.4 out of 5 stars 21
4.7 out of 5 stars 11
5.0 out of 5 stars 2
Price
$70.00$70.00
$49.41$49.41
$164.25$164.25
$193.06$193.06
$169.00$169.00
$119.00$119.00
$579.00$579.00
Best for
Camping
Camping
Backpacking and Camping
Backpacking and Camping
Backpacking
2-Season Camping
2-Season Backpacking
Dimensions
85 x 31 inches
—
72 x 25 x 4 inches
72″L x 21.5″W x 2.5″Th
72 x 22 x 2 inches
90.90 x 31.90 inches
83.1 x 32.5 inches
Weight
10 oz (284 g)
—
1.4 pounds
1.4 pounds
1.33 pounds
4.72 pounds
1 lb 7.7 oz (672 g)
R-value or Temperature Grade
Adds up to 25F of warmth
—
3.2
3.7
3.0
15°F (-9°C)
15°F (-9°C)
Non-PFAS
✔
✔
✔
✔
✔
✔
✔
About the Sea to Summit Reactor Sleeping Bag Liner
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.
thermolite
Imported
Insulated sleeping bag liner adds extra warmth and personal hygiene to any sleeping bag.
Hollow-core Thermolite EcoMade fibers are used in a grid-pattern fleece for maximum warmth retention
Drawcord footbox can be opened or closed for optimal comfort and integrates perfectly with the footbox of our Free-Flow Zip system in select Sea to Summit sleeping bags
HeiQ Fresh odor control technology helps keep the liner fresh even after extended use
A mummy shape designed for maximum thermal efficiency including shoulder zippers and a footbox drawcord for additional temperature regulation, Sea to Summit Guarantee is offered for the Lifetime of this product
Customers say
Customers find the sleeping bag liner provides good warmth, keeping cold air out and serving as a leg warmer, while being comfortable and functional. They appreciate its value, with one customer noting it’s worth the extra weight in the backpack, and another mentioning it functions as an effective barrier from the nylon sleeping bag.
Tom Maloy –
Works as it should. Easy to wash.
So pleased with this purchase! I used it every night on a 10 day backpacking trip and it was great! It was an effective barrier from the nylon sleeping bag, so I didnât stick to it and it was easy to clean when I got home.Also, itâs been great on other warm weather campouts when a sleeping bag would have been too hot.I think itâs definitely worth the spend!
robert docherty –
Amazing. Must have.
An absolute must for campers. It is insanely comfortable and warm. I am wearing as I write this review. I was shivering in camp last night under my down blanket. I woke up and put this bad boy on and slept like a babe the rest of the night. Love it. I have the breeze one for summer as well.
Brad K. –
Sleeping bag liner.
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.
Mark Kendrick –
Stay warm and cozy!
These really add extra warmth to your sleeping setup out in the back country. It’s very light and compact when stored away. The liner is super comfortable on your skin and doesnt feel weird at all.
daveNYC –
Extra warmth for minimal weight
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 5â+ of snow one night. This definitely helped keep me warm, especially sleeping on an ultralight foam pad.Packs down small and doesnât 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 doesnât get too much in the way of sleeping, this is a good purchase.
James Clay –
Keep you warmer
Added at least 10 degrees to my sleeping bag and only added a little extra weight
D Balliet –
Fan-freakin-tastic!
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!!
Amanda E. –
Great product
Iâm a cold sleeper so I was a little worried when the temp dropped way lower than seasonal normals on my last backpacking trip. I have a 20 degree bag with temps at 36. I purchased this liner and actually woke up sweating! Not only that, but itâs functional- I wore it all morning since your arms are out and you can raise it to a comfortable level on your legs. I would buy again and can imagine using only this during the summer!
Ian –
Great item, thank you.
Ambra Montebelli –
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.
Carecoco –
Lo devolvà porque pensé que tenga otro grosor. Este modelo no estaba suficiente grueso por lo que buscaba. No lo usé – pero con una mejor descripción dando todos los detalles, se podrÃa haber evitado este trámite
CpJws –
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RJ –
Super warm und kuschelig, genau was ich wollte.