Greetings from West Berlin, American Sector!
That's what I found about the question written by a well informed surplus shop:
A great choice for summer use, this lightweight bag also works together with the heavier bag. This is almost a direct copy of the Carinthia Tropen bag, with sli
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I don't own both and can't tell you so much about it. For sure I also know just the usual descriptions that you surely already could find yourself, but I did read of course a lot about the Carinthia sleep system Tropen / Defence 4, because it is issued to the German Army and used by a lot of German bushcrafters too and heavily discussed in German bushcraft forums.
I give you a surely unexpected answer to your question behind the question you asked here. The question which is the best modular sleeping bag system on the world market for civil use. I assume that is the question of most bushcrafters in temperate countries.
I bought the similar Snugpak Special Forces System, and I will tell you why:
The Asian made SF bivvy bag is outstanding light and compact packing. The flap of the zipper is constructed to sleep on the left side in the open if it's raining, what works very well, by the way and I usually don't set up a military poncho tarp if it isn't already raining in the evening. When I am in my bivvy bag it may rain outside, I don't care!
Because I use it mainly in France and Germany I want a zipper in the bivvy bag for better ventilation in warm and dry conditions, or under the tarp or military poncho and in a tent I can enter my sleep system better if the bivvy bag has a zipper anyway.
Apart from horribly hot summer conditions I always use the bivvy bag around my sleeping bag everywhere in order to keep it dry and clean.
The Carinthia bivvy bag is surely more durable, but far more expensive and constructed to sleep on the right side. I fall asleep better on the left. And I do not hop around in my sleep system, I don't need such a tough bivvy bag like the Carinthia Sleeping bag cover of the German army, or the British Army bivvy bag, which has a very wide entrance but no zipper, by the way.
But I admit, the new Goretex material of the Carinthia bivvy bag that seems to allow you to breath THROUGH the fabric, (the so called GAS PERMEABLE TECHNOLOGY, that is different to the fabric of usual Goretex bivvy bags) of the totally closed bivvy bag looks quiet interesting. That technique doesn't avoid condensation of breath moisture though and is more a military thing than of civil interest. I will always breath out of my bivvy bag anyway, I have no enemy who searches me with a thermographic camera, my only enemy is at the inside of the bivvy bag to water condensating breath moisture, because this can become very unpleasant and even dangerous in cold conditions.
The SF1 sleeping bag with the SF bivvy bag fits without compression bag well into a 7 litres Ortlieb drybag PS10 and this combination is outstanding light. I think it is the lightest sleep system with NATO stock number with this temperature rating. The Ortlieb bag is no military item but a civil high end quality German made dry bag.
The Snugpak Special Forces sleeping bags are made in a very high quality in Britain with a Swiss made filling, incredibly comfortable and well working. The olive green versions are cheaper than the camouflage versions, by the way.
I think the mainly Slovakian but also Moldavian made Carithia products are very well made too of course, as the stuff is issued to most NATO armies in Europe. But as I wrote I don't own current Carinthia sleeping bags.
So, until here you probably understand why I prefere the Snugpak Special Forces System for summer and 3 seasons use.
I carry an additional mosquito head net, the Carinthia Tropen has it built in, but due to this construction it has no central zipper. The zipper is located on the side here, but I prefere by far a central zipper.
Carinthia offers such a summer bag with central zipper too, the Defence 1 and a lot of other versions too of course, but I compare here the usually issued Carinthia system Defence 4 + Tropen + German army bivvy bag.
Now we compare Carinthia Defence 4 and Snugpak SF2.
The Defence 4 is very roomy. It is a very good option for a less sporty big guy. But a thin person or a more athletic build man needs to heat up a lot of air in it, and because it has no warmth collar, he will pump out the air with every motion. If you don't wear a padded suit in it anyway, this sleeping bag alone is relatively fresh inside, regarding volume and weight of it.
The Defence 4 is so big, that an athletic man in padded clothing and boots and in the Carinthia Tropen sleeping bag fits into the Defence 4.
The Snugpak SF system is constructed different: The man in boots and padded suit goes into the SF2, the warmer bag, and the SF1 goes over that. The sleeping bags on theyr own aren't really tight like a civil mountaineering sleeping bag, but tighter than the Carinthia bags, because the Snugpak System has an additional adapter, that belongs in between the zippers and makes them a few centimetres wider.
So without adapter the SF sleeping bags are tighter than with it, what makes sense, because we assume that the man will wear less on the person if he uses just the SF1 or just the SF2, but if he connects them both to reach a comfort temperature rating of -20*C he surely will wear a padded suit in it if he is a soldier in the field or a comfort orientated experienced civil outdoorsman.
Different to the Carinthia Defence 4, which is the outer layer in the combined system, the Snugpak SF2, which is the inner layer in the combined system, has a warmth collar! That is a very light but very effective part of the usual winter sleeping bag construction and this is missing totally in the Carinthia system Defence 4 + Tropen.
That's why I prefere the SF2 over the Defence 4, the Snugpak SF system over the issued modular Carinthia system.
But there is also a downside of the Snugpak system:
I need a rain or snow protected space to put the adapter into the both sleeping g bags. I need to pull them out of the bivvy bag to attach the 4 zippers to the adapter. In the end I just have to open only one zipper in order to enter or leave both sleeping bags. The bivvy bag has it's own zipper of course.
In the Carinthia system I just put the Tropen into the Defence 4 and that's it!
In this case the Defence 4 may stay in its bivvy bag while I am doing that.
I can keep the adapter in the SF2 or SF1 though, speed up the connection. But I have to pull the sleeping bags out to connect them anyway.
The point is, that one uses the warmer SF2 before one adds the SF1, but this goes between SF2 and bivvy.
So the Carinthia system is by far more handy to put together. But in every other point the Snugpak system is superior in my opinion.
Because both bivvy bags function very well you usually don't need to dry the sleeping bags separately. (Sometimes you need to shake ice out of the bivvy bag though.) But in some conditions, especially if you did breath by accident into the bivvy bag, moisture can build up in the outer layer of the sleeping bag insulation. You could avoid that with a vapour liner, regarding usual sweating, but that's surely not the most pleasant idea for normal use.
So, there is a risk to get a whet outer insulation layer. The thinner SF1 will dry faster than the thicker Defence 4 of course. If you can't dry it, you keep the relatively dry SF2 winter sleeping bag. That is another reason to choose the Snugpak system.
Who wants the Carinthia bivvy bag can combine it of course with the Snugpak SF system. The bivvy bags are too different to decide generally which is better than the other. It depends on the personal preferences and intended use.
The very warm Carinthia Defence 6 has a warmth collar, by the way, and others of their models too. But they don't really belong into the issued modular system.
I hope that helps.
Ultimate versatility was the aim of this systems design so that it suits any trip in any environment. You can use the sleeping bags individually or layer them together to cover all conditions. The Special Forces System WGTE gives you the Special Forces 1 WGTE Bag for use in above freezing...
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Snugpak® Special Forces Bivvi Bag lets you travel as light as possible, and be prepared to take cover quickly in adverse conditions. This is extreme camping. As the name suggests, this is a hard-working and reliable Bivvi
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