Does anyone have any first had knowledge of these liners? Taking the SO in a Kelty Cosmic 20 down bag and am thinking of adding this to it to make sure she isn’t cold. She also will have a Helinox cot and a S2S Comfort Plus SI pad…

If she gets cold sleeping, my trip is done…

Take a bunch of chemical heat packs, Brian . . .

boonie: "Take a bunch of chemical heat packs, Brian . . . "

As most folks around here have realized I am a bit more old school, many times I have taken a rock from around the fire pit and placed it in the bottom of my bag on really cold nights.

No experience first-hand with that one, but one similar in terms of warmth rating. It definitely added to the warmth of the sleep system altogether and also made a nice "blanket" of sorts when temps were too warm for zipping the sleeping bag up at night. Added benefit of keeping the inside of the bag clean which should help extend the life of the bag.

Only thing that is annoying is if you move a lot at night. It seems to want to move around a bit if you're always thrashing about.

My family and I often use bag liners. I have a Reactor, maybe not the "Extreme" model, however. They do a good job of making the bag more comfortable at lower temperatures. I've also found them to be very nice when it gets warmer and I want to open my bag up. It's like having a sheet, keeping the chill off, but still very comfortable. It also keeps the bags much cleaner. They're super easy to clean. I even had/have a silk liner which is amazingly warm for how thin it is. It doesn't stretch though. I find the stretchy liners more comfortable.

I just checked my bag liners. I do have the Reactor Extreme as well as an older Reactor and one in CoolMax. All are nice liners. The Extreme is extreme! Warm and comfortable. I like the others just as well though.

SlickNorthwoods: "Only thing that is annoying is if you move a lot at night. It seems to want to move around a bit if you're always thrashing about. "

This is me. I've tried liners, but decided I'd rather just wear mine.

I agree that when it gets chilly, wear what you've got and stay as warm as you can. The liners are a luxury (a very small, light, useful luxury). As I mentioned, when it's warm, I open up the bag and have the mummy liner around me as though it were the bag. When it cools down during the night, I just zip up as necessary.

When I wear all I've got along to stay warm, I'm bringing sweaty work items into an otherwise clean bag. I've done it that way, buy the liner is a very small item that puts one more layer between me and the cold.

A cap and socks are some of the first and best items to help retain heat in the bag at night.

Extreme Reactor makes it much warmer - how much is up to an individual.

boonie: "Take a bunch of chemical heat packs, Brian . . . "

If you are pushing the limits of your bag, this is the easiest way of making sure you are warm overnight. I always bring them (fall & winter), don't always use them.