Last updated at 10/06/2026 00:31:12
Sea to Summit Thermolite Reactor Extreme Sleeping Bag Liner - Red, 90 x 210 Centimeter
Free delivery
Affiliate Disclosure: We may receive a small commission for purchases made through this link at no extra cost to you. This helps support our site. Thank you!
Sea To Summit Reactor Extreme W/Drawcord Sleeping Bag Liner
Delivery $26.62
Sea To Summit Reactor Extreme Liner Compact Mummy w/ Drawcord
Delivery between 16β24 June $9.95
Sea to Summit Reactor Extreme Sleeping Bag Liner Compact Mummy w/ Drawcord
Delivery between 15β23 June $7.90
Sea To Summit Compact Mummy w/ Drawcord
Sea To Summit Thermolite Pro Reactor Extreme Liner Compact
Delivery $30.83
Sea to Summit Reactor Extreme Sleeping Bag Liner - Compact Mummy with Drawcord
Free delivery between 15β17 June
Sea to Summit Reactor Insulated Sleeping Bag Liner
Delivery between 14β18 June $13.73
Sea to Summit Reactor Extreme Sleeping Bag Liner Compact slaapzak One-Size
originally posted on seatosummit.com
Got to take this out a few times now, including a week up in the ADKβs for the eclipse after blizzard like conditions. I wonβt sleep without some form of liner so when I saw the updated designs, I knew I had to get one. Really helps keep your core body temp when changing in/out of camp clothes for the day/night. I really like the micro grid fleeece design and feel. Definitely adds a good bit of warmth and a ton of comfort that can lack when laying in a sleeping bag. Itβs been a really convenient for hammock use too. I like this one so much I bought the Extreme for when it warms up a bit.
originally posted on seatosummitusa.com
This was a great addition to my Spark Ultralight sleeping bag to give me a bit of an insulation boost for a cooler weather backpacking trip. For my purpose, this was a much better option vs. buying a warmer sleeping bag. My only complaint is the opening at the bottom. Seriously, who needs that? I certainly have no interest in walking around camp in my sleeping bag liner. There are better ways to keep warm when not in my tent. The opening with the drawcord just adds unnecessary weight, cost and an opening for a draft. Drop the opening, sew it closed and it will be perfect.
originally posted on seatosummitusa.com
The Sea to Summit Reactor Fleece Sleeping Bag Liner is a fantastic product and a much needed one for camping. It provides extra warmth on chilly nights, extending the usability of sleeping bag into colder seasons. The fleece material is so soft and cozy. itβs lightweight and packs down making it easy to transport. I used it when I went camping last weekend and i will say , this will be a best investment for those who go camping. Love mine.
| Variant | |
| size | Mummy Compact w/ Drawcord |
Sea to Summit Thermolite Reactor Extreme Sleeping Bag Liner - Red, 90 x 210 Centimeter
Free delivery
Affiliate Disclosure: We may receive a small commission for purchases made through this link at no extra cost to you. This helps support our site. Thank you!
Sea To Summit Reactor Extreme W/Drawcord Sleeping Bag Liner
Delivery $26.62
Sea To Summit Reactor Extreme Liner Compact Mummy w/ Drawcord
Delivery between 16β24 June $9.95
Sea to Summit Reactor Extreme Sleeping Bag Liner Compact Mummy w/ Drawcord
Delivery between 15β23 June $7.90
Sea To Summit Compact Mummy w/ Drawcord
Got to take this out a few times now, including a week up in the ADKβs for the eclipse after blizzard like conditions. I wonβt sleep without some form of liner so when I saw the updated designs, I knew I had to get one. Really helps keep your core body temp when changing in/out of camp clothes for the day/night. I really like the micro grid fleeece design and feel. Definitely adds a good bit of warmth and a ton of comfort that can lack when laying in a sleeping bag. Itβs been a really convenient for hammock use too. I like this one so much I bought the Extreme for when it warms up a bit.
This was a great addition to my Spark Ultralight sleeping bag to give me a bit of an insulation boost for a cooler weather backpacking trip. For my purpose, this was a much better option vs. buying a warmer sleeping bag. My only complaint is the opening at the bottom. Seriously, who needs that? I certainly have no interest in walking around camp in my sleeping bag liner. There are better ways to keep warm when not in my tent. The opening with the drawcord just adds unnecessary weight, cost and an opening for a draft. Drop the opening, sew it closed and it will be perfect.
The Sea to Summit Reactor Fleece Sleeping Bag Liner is a fantastic product and a much needed one for camping. It provides extra warmth on chilly nights, extending the usability of sleeping bag into colder seasons. The fleece material is so soft and cozy. itβs lightweight and packs down making it easy to transport. I used it when I went camping last weekend and i will say , this will be a best investment for those who go camping. Love mine.
I had the previous version of this, advertised to provide up to 25 degrees F of extra warmth. While I have been very satisfied with most of REI's products, this liner's claims of warmth were ludicrously optimistic. It might have increased my sleeping bag's comfort rating by maybe 5 degrees F. As a liner, it served its purpose - but it was just that, a liner. It's good if you want to protect your sleeping bag from sweat and body oils, but for warmth it is no good at all.
Really satisfied with the feel of the material, the durability, and effectiveness of the bag liner. I got the extreme version because I wanted to be able to pair it with my 20Β° bag and get more range and extend its life. I also planned to use the bag liner as a hot summer night sleeping bag. Itβs also much easier to wash than a sleeping bag. So itβs nice to use on the trip. Turns out my favorite use for it is as a summer bag. Itβs very small when packed compared to a sleeping bag and works well to keep you comfortable on a backpacking or bike-packing trip on warm nights
The old design of this product was perfect, and had a foot-box with ample room. The opening at the bottom of this new one, when closed, creates a knot that your feet will fight with all night. I will never want the foot-box opened because even when I vent my sleeping bag, I still want something covering my feet. The material is vented enough already. Plus, being the "Extreme" version... do we really want any holes in it for actually extreme winter situations? I don't.In addition, the new one has buttons and a now non-removable cord pull around the neck that you'll be rolling over all night. This new one is very uncomfortable. The taller cut of the flap along your chest on this new one is the only improvement.. otherwise I really wish they hadn't changed it.
Tested in controlled environment, at home, in November, thermostat set to where I would normally sleep cool and uncomfortable using summer sleep system. Added the Reactor Extreme to my kit and went to bed. Woke up cool, but not terribly uncomfortable so it took a little bit of the edge off. After giving it a lot of thought I believe that the material simply can't trap enough heat with as thin as it is to do much more than a 2-4 degree bump. As such, I can't imagine a use case where I would actually choose to put this in my pack. I believe that sleeping socks and cheap synthetic long underwear would work much better.
I bought this liner in February 2020 as part of my PCT thru hike sleep system. I've used this liner over roughly thirty nights, seven nights in a tent in the woods and roughly twenty three at home. When I use it outside I exclusively pair it with a Thermarest Caurus 32 degree quilt. Combined my sleep system should stretch in theory to seven degrees, as I use a quilt I assumed my base temperature rating with the liner would drop to 15 degrees. This was not the case.The first night I used this system outside, temperatures dipped to roughly 20 degrees. Although I wore long underwear and a hat in the system, I woke up cold twice during the night. I then used the liner in my system for three nights in the smokies and two in Shenandoah, where nighttime temperatures ...Β MoreI bought this liner in February 2020 as part of my PCT thru hike sleep system. I've used this liner over roughly thirty nights, seven nights in a tent in the woods and roughly twenty three at home. When I use it outside I exclusively pair it with a Thermarest Caurus 32 degree quilt. Combined my sleep system should stretch in theory to seven degrees, as I use a quilt I assumed my base temperature rating with the liner would drop to 15 degrees. This was not the case.The first night I used this system outside, temperatures dipped to roughly 20 degrees. Although I wore long underwear and a hat in the system, I woke up cold twice during the night. I then used the liner in my system for three nights in the smokies and two in Shenandoah, where nighttime temperatures hovered at thirty degrees. Again I wore a full long underwear set and hat, and again I wore up cold several times a night. I understand that a liner is not a sleeping bag, but if the liner does not lower a bag or quilts temperature rating below what it's rated for, it's difficult to justify spending seventy dollars on it.Regarding comfort, I will say the base fabric is excellent. Soft and stretchy it's a great way to avoid the clammy feeling of ultralight sleeping bag material against the skin, and does well to protect said bag from the natural oils and sweat on human skin. Again however, this liner has issues. Specifically, after sleeping in this quilt for thirty days total there is significant pilling in the fabric at the foot area. While I would expect this after a year of use, thirty days worries me.In sum, this could be a great liner, but it's temperature rating seems extremely off, and its long term quality is questionable.
Used this for the first time last week in Fall Creek Falls and the low overnight was about 31 or so. Paired with my new BA Anthracite 20 bag (also first time use). I do NOT like the cold and I consider lows in the 30s as the absolute lowest overnight temp I would choose to camp in. I was pleasantly toasty all night - never too hot - felt great! The liner is soft. My only complaint is that my legs and feet felt very restricted. The second night was around 45 or so degrees so I used the bag alone without the liner and discovered the restriction I felt the first night was due to the liner - not the mummy shaped sleeping bag. Perhaps some kind of stretchy material could be added to this liner from the hips down - even better if that fabric was βslickβ. If that could be ...Β MoreUsed this for the first time last week in Fall Creek Falls and the low overnight was about 31 or so. Paired with my new BA Anthracite 20 bag (also first time use). I do NOT like the cold and I consider lows in the 30s as the absolute lowest overnight temp I would choose to camp in. I was pleasantly toasty all night - never too hot - felt great! The liner is soft. My only complaint is that my legs and feet felt very restricted. The second night was around 45 or so degrees so I used the bag alone without the liner and discovered the restriction I felt the first night was due to the liner - not the mummy shaped sleeping bag. Perhaps some kind of stretchy material could be added to this liner from the hips down - even better if that fabric was βslickβ. If that could be woven into the existing fabric to retain the warmth but allow more freedom of movement without it βgrabbingβ onto your legs/PJ bottoms/socks that would be truly amazing. Giving this four stars overall due to the restriction I felt (others may not) - but would give it five stars for warmth without burning me up.
I absolutely love my Sea to summit camping supplies in reactor fleece, sleeping bag liner color orange mummy with drawcord. It keeps you warm in temperatures below 0Β°. It is so comfortable and yes, it really does. Keep you warm extremely warm. I would definitely recommend this product. I would definitely purchase this product again. οΏΌ
| Variant | |
| size | Mummy Compact w/ Drawcord |
Sea to Summit Reactor Extreme Sleeping Bag Liner Compact Mummy (Drawcord)
Discover the innovative features of Sea to Summit Liners, designed for optimal warmth and durability during your outdoor adventures. Thermolite Pro fibres are made with hollow fibres and ceramic elements. These absorb and reflect infrared rays from the body for extra warmth. In addition, the sheet bags are treated with HeiQ Fresh FFL, a biocide-free fabric that neutralises body odours. The yarns are made of 50% recycled Thermolite EcoMade and 50% Thermolite Pro fibres. Thus, these liners offer not only warmth and comfort, but also an environmentally conscious choice. The drawstring at the bottom allows an opening to be created for the feet. The oversized hood fits comfortably around the head or around your pillow for an extra soft night. Experience the power of innovation and durability with the Sea to Summit Liners for your sleeping equipment.
Discover the innovative features of Sea to Summit Liners, designed for optimal warmth and durability during your outdoor adventures. Thermolite Pro fibres are made with hollow fibres and ceramic elements. These absorb and reflect infrared rays from the body for extra warmth. In addition, the sheet bags are treated with HeiQ Fresh FFL, a biocide-free fabric that neutralises body odours. The yarns are made of 50% recycled Thermolite EcoMade and 50% Thermolite Pro fibres. Thus, these liners offer not only warmth and comfort, but also an environmentally conscious choice. The drawstring at the bottom allows an opening to be created for the feet. The oversized hood fits comfortably around the head or around your pillow for an extra soft night. Experience the power of innovation and durability with the Sea to Summit Liners for your sleeping equipment.
Discover the innovative features of Sea to Summit Liners, designed for optimal warmth and durability during your outdoor adventures. Thermolite Pro fibres are made with hollow fibres and ceramic elements. These absorb and reflect infrared rays from the body for extra warmth. In addition, the sheet bags are treated with HeiQ Fresh FFL, a biocide-free fabric that neutralises body odours. The yarns are made of 50% recycled Thermolite EcoMade and 50% Thermolite Pro fibres. Thus, these liners offer not only warmth and comfort, but also an environmentally conscious choice. The drawstring at the bottom allows an opening to be created for the feet. The oversized hood fits comfortably around the head or around your pillow for an extra soft night. Experience the power of innovation and durability with the Sea to Summit Liners for your sleeping equipment.
Discover the innovative features of Sea to Summit Liners, designed for optimal warmth and durability during your outdoor adventures. Thermolite Pro fibres are made with hollow fibres and ceramic elements. These absorb and reflect infrared rays from the body for extra warmth. In addition, the sheet bags are treated with HeiQ Fresh FFL, a biocide-free fabric that neutralises body odours. The yarns are made of 50% recycled Thermolite EcoMade and 50% Thermolite Pro fibres. Thus, these liners offer not only warmth and comfort, but also an environmentally conscious choice. The drawstring at the bottom allows an opening to be created for the feet. The oversized hood fits comfortably around the head or around your pillow for an extra soft night. Experience the power of innovation and durability with the Sea to Summit Liners for your sleeping equipment.
in 9 offers
The lowest price for Sea to Summit Reactor Extreme Sleeping Bag Liner Compact Mummy (Drawcord) right now is $87.21 at Telemark Pyrenees, compared across 9 retailers.
The all-time low was $84.87 on 14 Mar 2026 β today's price is 3% above the lowest ever. This is at or near its all-time low β a good time to buy.
Prices last updated 10 June 2026.
