Which sleeping bag liner should I choose?

28 thoughts on “Which sleeping bag liner should I choose?”

  1. Which liner would be the best in South America, specifically Argentina where the weather ranges from 20 degrees to 90 degrees?

    1. “G’Day Debby

      The liner I would recommend for use in temperatures from 20F (-7C) to 90F (30C) would be the Coolmax Adaptor.
      In colder temperatures, the Adaptor will increase warmth in a sleeping bag: its knitted fabric provides a three-dimensional structure which traps air and helps to keep you warm – this may add up to 10F / 6C to your sleeping bag.
      In warmer temperatures, the Coolmax fibers will wick moisture away from your skin, keeping you comfortable inside a sleeping bag – opening the side and/or foot zippers of a sleeping bag will provide ventilation as the temperature increases.
      As things warm up further, the stretchy Adaptor will provide a comfortable sleeping environment as you sleep underneath a sleeping bag opened up to be used as a ‘quilt’
      When it’s really warm, the Adaptor will be all you need – the sleeping bag will be superfluous.


  2. I am getting ready to leave for a backpacking trip for 11 months, going to 3 countries in Africa, 2 in Europe, 1 in the Middle east, and 5 in South/Southeast Asia. Obviously weight and compactability are concerns for me, but I want to make sure I get the right liner that will be the most durable and appropriate for the humid climates that I will be traveling in.

    Any suggestions would be greatly appreciated!


    1. G’Day Patrick

      There are two liners in our range which would work best for you:
      If light weight and compact packed size are most important to you, I would take the Silk Traveller,
      If stretch comfort is most important to you, and you can carry a couple of more ounces I would take the Coolmax Adaptor.
      Both will provide pleasant sleeping environments, both will wick moisture, and both will dry quickly.
      If you’d like more details, shoot me an email at info@seatosummit.com – I’ll be happy to expand on this



  3. I’m looking for a fleece sleeping bag liner that I can use in summer months alone on my hammock.The problem is where can you find one Ina 80″x39″ or 40 wide (closed)

    1. G’Day Jack

      Hammock camping is becoming more popular, and in summer, hammock users are discovering that a conventional sleeping bag is often simply more insulation than they need. Our Thermolite Reactor Liners are very popular for conditions like this.

      Unfortunately, we don’t make a liner which is 40″ / 100cm wide – the closest we come is the Traveller-shape liners, for instance the Coolmax Adaptor Traveller Liner which is 36″ / 92cm wide.

      If you drop me an email at info@seatosummit.com and let me know the temperatures/conditions you’ll be sleeping in, I’ll be happy to make recommendations



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  5. Hello,
    This summer I am going on the Camino de Santiago de Compostela – Camino Frances in August for 33 days. It is mostly warm/hot nights with colder nights in the mountains. I recently purchased the Premium Stretch Knit Expander Liner and was wondering if this could be used alone or not in this kind of weather…It is so light and comfortable that I would prefer this as opposed to my 600g sleeping bag.

    1. G’Day Hol
      Thanks for taking the time to write to us about using a liner instead of a sleeping bag on the Camino de Santiago de Compostela.
      A liner can be used instead of a sleeping bag in warmer weather; especially if you are sleeping indoors where there is unlikely to be much air movement (if you were to sleep outdoors, moving air would pass through the fabric of the liner and take away the warmth you have generated). Most end-users would use the warmer Thermolite Reactor or Reactor Extreme for the kind of use you’re suggesting, but in the refugios and albergues the overnight temperature shouldn’t drop below 15°C/60°F at night, and at these temperatures the Expander would (just) be adequate.
      If the temperature drops much below 15°C/60°F, you would need additional insulation. I would certainly consider the new quilt-style Traveller sleeping bag (390g/13.7oz) for such a trek.
      I trust this information helps – if you’d like more details, please email us at info@seatosummit.com and put the word ‘Camino’ in the subject line


  6. I just got a Trek TKI as my first summer bag. It’s great! A big selling point for me was the generous cut because I am a bigger fellow (6 ft 3 in, 210 lbs.) and a stomach sleeper — I usually have one knee and two elbows bent. I am considering a S2S liner to keep the bag clean and to extend the temp range of the bag down below its 40 degree F rating. I sleep a little cold. Two questions: (1) which is the best choice for liner? and (2) do all liners open only at the top? I have used liners before and I don’t like having to climb into one end of it. Thanks!

    1. Glad to hear you like your Trek Tk I sleeping bag – it’s been very popular with consumers looking for a little more room in a bag.

      Here’s the story with the temperature rating on the Tk I and the use of a liner to extend that rating downwards:

      The Comfort rating for the Tk I under the EN 13537 test protocol is 41°F or 5°C. As someone who sleeps a little cold, this is a good rating for you to use; for someone who may sleep a little warmer, the Lower rating of 32°F or 0°C would be more appropriate.

      Adding a Thermolite Reactor or a Thermolite Reactor Extreme would boost these ratings downwards so you would comfortably sleep in frosty conditions. They are both extremely stretchy – so much so that you won’t feel constricted inside the liner at all. However – they only have an opening at the top; a side opening would require a zipper which would significantly increase the weight and packed volume of the liners.

      One other thought – if you are using a sleeping bag in below-freezing temperatures, it’s essential to have a sleeping pad with an appropriate degree of insulation. We’d suggest an R-Value equivalent (the rating for insulation value) of 4 or above. Using a summer-appropriate sleeping pad (with an R-Value equivalent of 2 or less) will lead to you losing heat into the cold ground (which may be colder than the air temperature on any given night).

      I trust this information helps – please let me know if I can be of further assistance

  7. I am looking for recommendations for a liner for this sleeping bag. I know the review that I read on the bag does not mention needing any liners, but after reading your information here I want to protect my investments! These bags are not cheap anymore and since it will be two of us in the sleeping bag, I definitely want to protect it. What kind of liner would you recommend for that bag?

  8. Hi, I’m trying to work out whether to go for a down or synthetic sleeping bag, and what liner to buy. So far I’m more keen on a three season down because weight is a priority, but I’m worried about getting too hot in the summer and sweating into the down- would Your silk liner help to keep a Down sleeping bag dry, or would it Wick moisture away from the skin and into the Down, making it more wet?

    1. G’Day Katie

      First of all, our apologies for the delayed response – we’ve had some issues with emails not being forwarded to us via the blog.

      You ask some excellent questions about sleeping bag performance and comfort and about how liners function. A thorough answer to these questions would be quite long and complex (and I’m including an email address below if you would like to discuss things further) – for the moment, here are some ‘bullet point’ comments:

      – An ideal ‘three season’ sleeping bag has the ability to be opened up for ventilation. This may include a secondary zipper or drawcord which allows the footbox to be opened, and permits the sleeping bag to be used as a quilt or comforter. Good examples include the Micro Mc II and Mc II. This flexibility means that you should never be too warm in a sleeping bag – yet you will have the ability to close the zippers, cinch up the drawcords and stay warm when outside temperatures are cooler.
      – A silk liner (or indeed the Coolmax Adaptor Liner) will wick perspiration away from your body, and spread it over a broad area where it can dissipate. (If you are not using a wicking liner, your perspiration will tend to concentrate on small contact areas such as your shoulders and hips, which can therefore become clammy). The moisture which has been wicked away from your body by the line will dissipate through the down or synthetic insulation in the form of moisture vapor, so it shouldn’t cause the insulation to get wet merely by passing through it. In colder conditions, this moisture vapor will condense on the inside of the sleeping bag shell (regardless of how ‘breathable’ that shell might be – this is the primary reason for airing a sleeping bag in the morning). A new type of down technology can reduce the effect of this – see the next point.
      – All Sea to Summit sleeping bags are equipped with UltraDry Down which will prevent moisture being absorbed into the down to a great extent. Some other manufacturers offer ‘dry’ down products – going into the details of this technology falls into the category of ‘further discussion’ as mentioned earlier.

      In summary, if you purchase a quality ‘dry’ down sleeping bag which has the option of adequate ventilation, and you pair it with a wicking liner (either silk or Coolmax), you have the basis of a sleep system which will work across a broad spectrum of temperatures. And if you include a sleeping mat in that lineup which has the right level of comfort and an appropriate level of insulation, you will have created an ideal sleeping system.

      If you’d like to discuss this further, drop us a line at marketing@seatosummit.com and put ‘Sleep System questions’ in the subject line of the email



  9. Hello. I’m looking for a silk liner that will fit into two mummy sleeping bags zipped together. Is the double silk liner my only option? I’d prefer not to do additional sewing, but it seems unavoidable since neither Sea to Summit nor any other sleeping bag liner manufacturer seems to make a liner for two joined mummy sleeping bags.

    1. G’Day

      Thanks for your question regarding a ‘double mummy’ liner. Sorry it’s taken a while for us to respond; we’ve had some technical issues with the blog.

      I’m sorry to say that beyond the rectangular Double Premium Silk Liner, we don’t make a liner specifically designed to accommodate the contours of two zipped-together sleeping bags (which come in many different shapes and formats).

      Sorry we can’t help you here!



  10. Is there any actual accurate independent testing done on your thermolite or did you just guess? I’ve used one in the bush while hunting ( the extreme) and it did virtually nothing, for sure maybe 2 deg but never 14, I ended up removing it and getting a set of thin thermals on, much warmer than your product, over all I felt very disappointed in the purchase and so do a few other hunters I know.

    1. G’Day

      Thanks for taking the time to write to us about the Reactor Thermolite Liners. Sorry for the delay in replying – we’ve had some technical issues getting emails forwarded through the blog.

      In answer to your question, there is no standard by which sleeping bag liners are rated (unlike sleeping bags which are increasingly being rated using a European Standard – EN 13537 – which uses heated mannequins in sleeping bags in a cold chamber). Having said this, a lot of sleeping bags are still not rated according to this standard, and a sleeping bag manufacturer is free in the US to put whatever ‘rating’ on a bag that they choose.

      At the time when the Reactor Liners were introduced, a lot of ‘real world’ testing was done, and individual testers reported their perceptions compared to the (then standard) baseline silk liners. An addition of up to 8°C / 14°F was held to be realistic from these tests.

      However, there are huge variations in sleeping bag construction (which may lead to significant heat loss through cold spots in the bag), and huge variations in the actual insulation value of a sleeping mat (and heat loss into the ground is often the greatest source of cold for a sleeper). A thermal liner can only compensate for these factors to a certain degree.

      You’ll find some more thoughts on this topic here:


      I trust this information is helpful; if you’d like further details, drop us a line at marketing@seatosummit.com



  11. What sleeping bag liner would suit a camp? I’m not sure exactly how many degrees it will be at night but could you recommend one ? Also not too pricey please

    1. G’Day Laurel

      Thanks for your question about finding the right liner for use in camp.

      I’m going to make a couple of assumptions here:

      – It sounds like you are static camping/car camping rather than backpacking
      – It appears that you may want to add a little warmth to your sleeping bag

      (If either of these assumptions are incorrect, shoot me an email at info@seatosummit.com and put ‘Sleeping bag liner – follow-up’ in the subject line)

      Our recommendation for an inexpensive liner which will add a little warmth to a sleeping bag as well as keeping that bag clean would be the Expander Liner. This is made of a stretch material which is really comfortable – you won’t even feel that you are sleeping in a liner. It will trap a little extra air in your sleeping bag which will add some warmth, but not as much as you would expect from one of our higher-priced ‘technical’ Reactor Thermolite liners. The Expander series weighs more and has a larger packed size than the ‘technical’ liners; but if you are car-camping, this wouldn’t be an issue.

      I trust this information is helpful – please drop me a line at the above email address if I can assist you further


  12. what sleeping bag liner should I use for a scout camp. I’m also a girl so anything that would keep me warm would be alright. Bearing in mind I sleep with 1 leg bent and 2 arms bent. Thanks

    1. G’Day Gazelle

      Thanks for taking the time to write to us about the right type of sleeping bag liner for use at a Scout camp.

      It sounds as if you have a sleeping position which would be best accommodated by a stretchy liner. And, given the fact that you would like the liner to add some warmth to your sleeping bag, our hands-down recommendation would be for the Thermolite Reactor or the Thermolite Reactor Compact Plus.

      Both of these liners will add warmth (the Compact Plus will add a little more than the standard Reactor) and they are very stretchy, so they will create a very comfortable sleeping environment. They are also extremely easy to take care of – if they get dirty (which can occur at a Scout camp), you can take them home and wash them in a washing machine with normal laundry soap.

      I trust this information is helpful – if you have further questions, shoot us an email to info@seatosummit.com and put ‘Sleeping Bag Liners – further questions for Scout camping’ in the subject line.



  13. For camping in Europa with temperaturen around 20 celsius which liner works best ? Is there much difference between the thermal extreme and reactor fleece liner as stand aloen use inside a tent? I am 6ft tall?

    1. G’Day Babette

      Thanks for your question regarding use of a liner as a ‘stand alone’ sleeping bag in summer temperatures.

      At 20°C, either the Reactor Extreme or the Thermolite Fleece Liner should provide a pleasant sleep environment. The Thermolite Fleece Liner will be warmer than the Reactor Extreme, which might be helpful if the temperatures should drop lower than expected.

      The Thermolite Fleece Liner does have a 1/3 length zipper, and is therefore a little easier to get in and out of.

      One thing to bear in mind is that neither of these liners is windproof, and therefore if you were to sleep outside in a place where moving air is a factor you would need a windproof barrier (perhaps a light bivy bag or sleeping bag cover or a poncho which could be used as a cover). If you are sleeping inside a tent as you mention, this should not be an issue.

      Both liners are also machine washable, so if your camping plans include sandy areas (beaches, dunes or river banks), a liner is a much simpler thing to clean than a down sleeping bag once you get home.

      I trust this is helpful



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