Sea to Summit Reactor Extreme Sleeping Bag Liner - 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 25 offers
The lowest price for Sea to Summit Reactor Extreme Sleeping Bag Liner - Mummy (Drawcord) right now is $66.99 at Bay Sports, compared across 23 retailers.
The all-time low was $65.00 on 17 Nov 2025 — today's price is 3% above the lowest ever. This is at or near its all-time low — a good time to buy.
Prices last updated 16 June 2026.
Last updated at 16/06/2026 23:25:48
Reactor Extreme Sleeping Bag Liner - Sea to Summit | Bay Sports Standard
Delivery between 18–26 June $9.99
Sea To Summit Reactor Extreme W/Drawcord Sleeping Bag Liner
Delivery $26.80
Sea To Summit Reactor Extreme Liner Mummy w/ Drawcord
Delivery between 23 June – 1 July $9.95
Sea to Summit Reactor Extreme Sleeping Bag Liner Mummy w/ Drawcord
Delivery between 22–30 June $7.90
Sea To Summit Reactor Extreme Sleeping Bag Liner - Mummy w/ Drawcord
Delivery between 22 June – 1 July $10
Sea To Summit Reactor Extreme Sleeping Bag Liner
Free delivery
Sea To Summit Reactor Extreme Sleeping Bag Liner (regular) - Free Post
Free delivery
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Sea To Summit Reactor Extreme Unisex Sleeping Bag Liner - Standard
Free delivery
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Sea To Summit Reactor Extreme Sleeping Bag Liner
Free delivery
Sea To Summit Reactor Extreme Sleeping Bag Liner Standard Mummy with Drawcord
Delivery $10
originally posted on seatosummitusa.com
Truly impressed with the quality of this liner; perfect for campers and outdoor enthusiasts alike. Super lightweight but also relatively warm, so it’d make a great addition to your camping supplies. Could probably double as a sleeping bag in the summer! Overall, I definitely recommend.
originally posted on REI
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.
originally posted on seatosummitusa.com
I bought mine on sale and am happy with the purchase. I've used this liner for a couple of years now for occasional spring, summer and fall camping/cottage living. I view it as a functional, warmer version of a typical sleeping bag liner. In very warm weather, I can use it as a standalone cover (sort of like being in bed with just a sheet over you). But it does not give 15 degrees C of extra warmth to the sleeping bag as the weather gets colder. For instance, I cannot imagine it turning a 10 degree C bag into a -5 degree bag. The regular price seems a bit high for what you get, especially considering that it is made in China. I have not used it for backpacking where weight is more of a concern.
| Variant | |
| size | Mummy Standard w/ Drawcord |
Reactor Extreme Sleeping Bag Liner - Sea to Summit | Bay Sports Standard
Delivery between 18–26 June $9.99
Sea To Summit Reactor Extreme W/Drawcord Sleeping Bag Liner
Delivery $26.80
Sea To Summit Reactor Extreme Liner Mummy w/ Drawcord
Delivery between 23 June – 1 July $9.95
Sea to Summit Reactor Extreme Sleeping Bag Liner Mummy w/ Drawcord
Delivery between 22–30 June $7.90
Sea To Summit Reactor Extreme Sleeping Bag Liner - Mummy w/ Drawcord
Delivery between 22 June – 1 July $10
Truly impressed with the quality of this liner; perfect for campers and outdoor enthusiasts alike. Super lightweight but also relatively warm, so it’d make a great addition to your camping supplies. Could probably double as a sleeping bag in the summer! Overall, I definitely recommend.
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.
I bought mine on sale and am happy with the purchase. I've used this liner for a couple of years now for occasional spring, summer and fall camping/cottage living. I view it as a functional, warmer version of a typical sleeping bag liner. In very warm weather, I can use it as a standalone cover (sort of like being in bed with just a sheet over you). But it does not give 15 degrees C of extra warmth to the sleeping bag as the weather gets colder. For instance, I cannot imagine it turning a 10 degree C bag into a -5 degree bag. The regular price seems a bit high for what you get, especially considering that it is made in China. I have not used it for backpacking where weight is more of a concern.
I went to Central Idaho for a seven day, six night elk hunt. Temperatures were projected to drop into the teens and low 20s most nights. My Kelty sleeping bag is rated to 20 degrees, but as we all know, that is not the comfort rating. I purchased this liner hoping it would give me the warmth I needed each night. It worked great. There was not a single night when I felt cold. Instead, I was truly warm.
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.
This thing is great for an added layer of warmth. It is lightweight and feels like a sheet inside your bag or quilt. Not sure yet on how much it adds thermally, but is good to fill those gaps around you to improve the bag’s efficiency. Is it a placebo effect? With it being as thin as it is, it does make you feel warmer by having more fabric contacting your skin. It also helps keep the bag/quilt cleaner which is a huge benefit.
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 ... 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.
We loved this product because it kept our sleeping bags cleaner, warmer, but also was nice during hot weather. The one reservation I had before using it was its lack of a zipper. I thought it would be hard to get in and out of it. Also, I tend to like the feel of my down bag, and I thought the liner would ruin this "cozy" feeling. However, both of these issues were no problem.First, the liner was a nice way to keep our bags clean. We got pretty grungy during this trip, and having a layer to protect the bag was nice. I don't know if I even need to wash our bags after the trip. Also, the liners added a lot of warmth. I have a 30 degree bag that would have been too cold for a number of the nights. Craig has a 20 degree bag that also kept him warm. There were no ... MoreWe loved this product because it kept our sleeping bags cleaner, warmer, but also was nice during hot weather. The one reservation I had before using it was its lack of a zipper. I thought it would be hard to get in and out of it. Also, I tend to like the feel of my down bag, and I thought the liner would ruin this "cozy" feeling. However, both of these issues were no problem.First, the liner was a nice way to keep our bags clean. We got pretty grungy during this trip, and having a layer to protect the bag was nice. I don't know if I even need to wash our bags after the trip. Also, the liners added a lot of warmth. I have a 30 degree bag that would have been too cold for a number of the nights. Craig has a 20 degree bag that also kept him warm. There were no issues with getting in and out of the liner, and we just kept our liners in our sleeping bags when we packed them in our stuffsack. We used our liners in super-hot weather (100 degrees) by sleeping on top of them and then using them as a sleeping bag when it got cooler in the middle of the night.Overall, this is a really nice product, and I would highly recommend it. I think that the amount of warmth from the bag was just right for a broad spectrum of temperatures (20s to 100s).
Just went on a 3 days camping trip using my traverse IIv -4 sleeping bag and this liner inside. I am always cold, but this liner really warmed up the bag and made it toasty. Waking up to -3 celsius in the morning, I didn't want to get up because it was so nice inside my bag, liner and tent.For me, I will get down booties though as my feet are never warm.Highly recommended and it is light and packs small.
| Variant | |
| size | Mummy Standard w/ Drawcord |
