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Sea To Summit Thermolite Reactor Plus Compact-Length Mummy Liner


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Thermolite Reactor Plus Compact-Length Mummy Liner

Extend the life of your sleeping bag and trap a little extra warmth with the Sea To Summit Thermolite Reactor Plus Compact-Length Mummy Liner. Built with insulating Thermolite fabric, this liner traps heat without over-bulking your pack. Furthermore, it keeps the inside of your bag clean and gives it a break from the wear and tear of normal use.
  • Sleeping bag liner adds a little extra warmth to colder nights
  • Drawcord hood for facial protection
  • Comes with lightweight Ultra-Sil stuff sack
  • Item #STS0114

Thermolite (80g), [core and foot box] Thermolite (110g)
Degrees Added
20 F
36 x 72 in
Claimed Weight
9.3 oz
Recommended Use
staying warm
Manufacturer Warranty

Tech Specs

What do you think about this product?


>Rating: 4

Adds a little warmth!

This liner is a great way to add a bit more warmth to your mummy bag. It is compact and lightweight which makes it a perfect addition to alpine backpacking. It is a great product however, at 5' tall, the liner has quite a bit of spare room at the bottom.

>Rating: 4

20 Degrees?

I've used it several times

Ok. This is a pretty cool liner and made my 30 degree synthetic nice and warm when I was out and 8 inches of snow fell on us overnight. Granted the temperature was fairly moderate (25ish?) that night and the liner is supposed to give an extra 20 degrees. I would say treat as if it is giving you an extra 15 and you won't ever be disappointed. I definitely liked that I was warm and toasty waking up at 5 am to get going to our next spot. I must admit it was tough getting out of my warm bag and into the cold to attempt to move snow. I think I will actually use this while hammock camping mid-summer too as a stand-alone.

>Rating: 5

Turn your sleeping bag into a 4 season

I've put it through the wringer

I bought this to get my 0 degree even more toasty and my Marmot Hydrogen into a true 4 season sleeping bag. Weighing in at 9.3 oz, it is not the lightest liner. Does it actually add 20 degrees? Not sure. Did it make me noticebaly warmer? HECK YES! I camped in the single digits in Northern MN a couple Thanksgivings ago. I had my zero degree bag with me and combine with this liner, I slept comfortably in only boxers. Yes, just my boxers in single digits. Using this with my Marmot Hydrogen it brings the bg down to a 20-22 degree bag on paper. Again, I am not sure if it truly adds 20, but it for brings a noticeable warmth. It turned my hydrogen into a 4 season bag which makes me happy because I love my Hydrogen bag. I have used it also as a sleeping bag in the summer and was comfy as well. In the spring, I have slept on top of my 55 degree synthetic and use the liner as a blanket. Definitely worth its price and the late fall and dead of winter is where this liner shines. I plan on getting the one above this liner (adds 25 degrees) for my wife.

>Rating: 4

good liner

I've used it once or twice and have initial impressions

I recently used this on a trip down the Blue Ridge Parkway. I have a 30 degree bag and knew the temperatures would be in the the 30s at night. So I decided to buy this and it was a life saver! I run pretty cold. And I was so comfortable with this with minimal clothing. I was comfortable all night with this liner, and if I didn't have it know I would have been freezing. My only problem was that I am 5'6 and wish it was just a little bit longer.

I recommend Not getting the "Compact" model if you want something Longer. It says on the Packaging that its for Women & Children.

>Rating: 4

Compact and warm - worth it

I've put it through the wringer

Owned this for over a year now, and I have to say I'm happy with it. It won't blow you away--there is only so much warmth you can expect from something only a little bigger than a soda can, but it makes a nice difference. I couple this with a 40 degree bag and it makes a warmer, more compact sleeping arrangement than a 20 degree bag, I think. It also keeps the bag clean, which is nice when I am cold and want to wear my dirty clothes in the bag. The only thing, I'm 5'11" and I would have gotten a slightly longer version if I could, it's just barely tight with when I try to shut the mummy and lie flat. All in all, I think it's fairly advertised, it's comfortable and keeps me warm enough that I always bring if it even might get cold.

>Rating: 1

Not impressed

I've used it once or twice and have initial impressions

I do alot of winter and shoulder season hiking. I had a recent issue with my 0 degree synthetic bag where I chilled over night and was very uncomfortable, so on the next trip I picked up a reactor plus and tried it out. needless to say I can't see how they can tout this liner to add 20 degrees to the bag rating. Was I slightly warmer? it's hard to say, meaning I didn't notice a difference and I was still cold over night. Almost seems like a gimmick to me. I'm keeping it for a warm weather lite liner.

Dude, your body has to produce heat for a liner or even an 850-fill sleeping bag to retain heat. Don't do the things that cause your body to generate heat before you get into a bag, you'll be cold in very cold weather. That is a user error, not the fault of the bag. I too do regular winter camping, on snow & on dry or wet ground, down to -10F. I appreciate the Reactor's fleece when I first get into my non-fleece lined 0F bag, and I do find that I stay a bit warmer using the reactor. Perhaps best yet, my body's oils & dirt transfer to the reactor, which is easily washable while my beloved 0F 800-fill bag stays clean. What to do to generate heat BEFORE getting in your bag? Think: drink some hot (non-alcoholic) liquid. Eat, esp. fats. Go for a brisk walk that gets your metabolism going. Soak in a hot spring. Put a Nalgene bottle filled with very warm water into your bat. And of course there is sex, but that is problematic at 0F...!

Yeah Mike, you're definitely from "PDX".

>Rating: 5

Perfect to extend your bags season

I don't have a need for a winter sleeping bag but I do like to camp in the shoulder seasons when temps can drop down to the 30's. I picked up the reactor liner for myself and the reactor plus for my wife. If you really want the extra warmth i'd grab the reactor plus. Its noticeably thicker and does add substantial warmth (Sea to Summit suggests it adds 20 degress while the reactor adds 15). Again, extra comfort, keeps your bag clean, and adds warmth for 9oz. I was on the fence on if this was worth $60 but it is totally worth it. You can also use it as your bag in the summer or take it on travels when you don't trust the bed sheets.


Will this liner work for both left and right zip mummy style sleeping bags?

Yes. They are open at the top so it does not matter what side your bag zips. These liners are a great addition to any sleeping bag. Keeps them clean and adds a little extra warmth. Best part is that you can have your bag unzipped to breath when in warmer temps with out getting darn right cold. Hope that helps!


Can this be machine washed?

Can this be machine washed?

Sea to Summit Care Instructions: Care of Sea to Summit liners is very simple: unlike some synthetic waterproof / soft shell fabrics which have to be washed in special non-detergent soaps, the liners can be washed in a home washing machine using normal detergent (referred to as laundry ?soap?). If you are using a top-loader washing machine, we would strongly suggest putting the liner inside a pillow case to prevent the impeller (the spiral plastic rotating column in the drum of the machine) possibly snagging the draw cord. A front-loader is much gentler on your gear, and this step is unnecessary. In either case, use the delicates or gentle cycle. Fabric softener will decrease the wicking performance of the fabric, and should be avoided. Do not dry the liner in a dryer; excessive heat can damage the fabric ? air-drying is the way to go.

Always use plant based soaps and fabric will last longer and stay stronger. I think that also applies to things like skin and produce..