Sea to Summit Thermolite Reactor Extreme Liner

The Reactor Extreme is quite roomy, unlike many bag liners which can often times be very restricting, however, the 25 degree added warmth rating is a real stretch IMO. More like 15* at best. And it’s fairly heavy at 14 oz, nor is the $70 price really that cheap.

sierra.com has roomy (64″ shoulder) Alps Mountaineering microfiber liner on clearance for $17, and truth be known it’s probably about as warm as the Reactor, in spite of the claims made by S2S. The AM Viper also weighs about 14 oz. Just take along a very cheap 1.7 oz pocket space blanket from Walmart to put over top if you get a little cold.

https://www.sierra.com/alps-mountaineering-viper-microfiber-sleeping-bag-liner-mummy~p~858pv/?filterString=sleeping-bags-and-pads~d~208%2F

I used this on the JMT when a cold storm hit us. 15F lows, winds, snow, etc. We added the Reactor Extreme(14oz) and a Reactor Compact(11oz). To our Rei Magma Quilt(30F) and REI Flash(32F) bag. IME the Extreme added about 8-10F and the Reactor added about 5F max. If in this situation again I am taking a Costco down blanket that I have modified with snaps. 16oz.

Thanks very much for your comments!

tried it with a reactor xtreme and froze my butt off while lending my bag to someone else.  temps probably were middle 50s and i slept on a NeoAir xlite (good R value) and inside a tent.  Had long underwear tops and bottoms on.  The material isn’t thick, like a very thin fleece.  I like S2S but think this product is snake oil.  And the weight just doesn’t make sense.  my 2 cents.  My 40F down quilt weighs the same…  I would get a 50F quilt and have actual insulation (loft) when needed.  Or don’t spend any money and just bring your light puffy instead of the liner and sleep in clothes.  that would be warmer than the liner IMO.

Yeah, by itself, it’s barely a slumber-party, sleep in the 70F living room bag.

Maybe on a Hawaii beach?  In summer.

As a liner, you certainly get another 10F, maybe, just maybe another 15F.  No way do you get their claimed 25F.

The weight and cost isn’t worth the warmth compared to just getting a higher rated bag/quilt.  But if you’re looking to extend the use of a marginal bag that you already have, keep the sleeping bag cleaner, or keeping a spouse happy is more important than BW, it could have a role.

How about mid- or heavy-weight thermals instead?

Instead of the S2S liner by itself in very mild conditions or as a “liner” to add warmth and cleanliness to a bag/quilt?

Back before Ray Jardine had cut off his first brand-name logo patch, I did a 9-day High Sierra trip with no stove, tent or sleeping bag.  Had a tarp.  Put on all my clothes (expedition-weight Patagonia PP UW top& bottoms, pile, beanie) on at night and slept on an orange Therm-a-rest (I was being stupid, but not an idiot).  It was fine at 40-45F.  At 30-35F, I didn’t sleep so well after the hot rocks from the campfire had cooled off.

Point being: How many more clothes would you have to bring to just sleep in all your clothes at night?  The better warmth/weight clothes we use would do more for you than the S2S liner.

Depends on the expected overnight low temps? You mention nothing about location, sleeping elevation, etc.

I have a SOL Escape Bivy that I have turned into a quilt.  Probably just as warm or warmer than the others.  Weighs less.  Will cut wind and light moisture.  It can get a bit clammy inside if it is warm but with it as a quilt I can vent.