X-Lite 200

>Initial research on Reddit has shown that the sleeping bags are usually 5-7 °C colder than specified, so it seems it won't be too warm then :) Good luck. Bags are rated using EN13537 / ISO23537 norms. Basically, they measure the heat resistance (how well the bag isolates, how slowly the heat leaks through it) in certain conditions, then the results are translated into a set of user-friendly temperatures. The crucial ones for you are the comfort and limit rating. You need to spend some nights outside in ISO-rated bag and observe how well and in what conditions you sleep, to learn what is your personal adjustement to those ratings. Some people need thicker bags, some do not. Air humidity, your fatigue, what and how warm you had for dinner / supper - it all matters and changes personal needs. There were nights when I slept in -2 C - -3 C temperatures in fully open bag (450g 700 CUIN down) just in base layer and there were nights when I had to fully close it when the temp was about +5 C. If you don't plan to camp in mountains I'd go for cheap and small synthetic bag ISO-rated for comfort about +10 C. Going for a high-end, expensive ones when you don't know what you need is kinda pointless to me. Whatever you choose make sure it has long zipper to open the bag fully and use it like a quilt if needed. Furthermore, you don't mention what is your goal. Do you need a bag that is super small when packed? Do you need it really ultralight? Do you want it to last for many years? Or do you just need anything but have too much money? PS go for quilts if you want wiggle room, in summer, outside of mountains you won't have to deal with cold draft, but don't forget to have a pad compatible with it. If you want the stuff really light and small, then when it comes to polish manufacturers, forget the quilts (they are heavier and pricer). Go for the Pajak Radical ULZ or Cumulus XLite 200. More budget-friendly would be some lighter variant of Fjord Nansen Svalbard Goose.

Just for the summer I'd go with +10 C comfort one. Smaller, lighter and more comfortable on warm nights. In such temps any sleeping pad will work, you don't need to care about R-value at all, just the comfort. While it's not convenient, even a fleece blanket would work in such temps. In polish lowlands +5 at the coldest point in July is like the 30-year lowest. I guess climate in Brandenburg is pretty similar and it such bag should easily work in summer up to 1000m asl. >(...) at the end that a bag rated down to +5 °C comfort will be okay on flats in summer if opened? Should be. For me, -5 comfort bag was unbearable on warm nights. When it got to like +20 C I wasn't even able to partially cover myself with it (like with a blanket). But +5 shouldn't be that hot. >Or are flats/mountains conditions mutually exclusive in the high summer? If you go high in Alps or Caucasus? Sure - almost. 3000m asl means 18 degrees lower temperature just due to higher altitude and lower pressure. If you sleep on / below / next to glacier, the air may also be slightly colder. In mountains the weather is way more unpredictable and you have to suck it up and deal with too warm bag when sleeping at the bottom. But generally, no. There are tons of mountain ranges in Europe that are barely above 1000, 1500 m asl high. In high summer, mid-july to mid-august (climate changes lately messed up the weather patterns a bit, I know) you should easily get away in them with +10 C bag, just use some thicker pad that has R-value at least 1.7-2. If you are pretty unlucky and get caught in colder night, wearing extra clothes will help (or covering the bag with them, down hoodie works perfectly for this!). In emergency, you can always use the NRC (mylar, like in the FAK) foil or put some hot water into the bottle, cover it with clothes and put it under your arm pit. You can survive near-freezing night in +10 C comfort rated bag, but you won't rest at all on that night and it will be huge PITA. Personally, I like the cheap (guess, 50-100 EUR nowadays?), beater synthetic +10 C bag. Aside from being good and cheap starter, it's a great bag for summer kayaking trips or even for trips where I won't hike, but will sleep somewhere under the roof and needing own sleeping bag. It's cheap so I don't care generally about it. Some even have integrated bug net! 0 - +5 C comfort is a good range for light, down sleeping bags. Warmer part of spring and autumn, whole summer. Great if you plan to spend more time biking or hiking in lower mountains and you want it pretty light and small (lightest ones like Pajak ULZ or Cumulus XLite 200 weigh like 320-350g and compress extremely well). Synthetic bags need way less compression cycles to degrade compared to down (compressing them is what kills them the fastest, assuming that you wash your bags from time to time). Down bags using so-called 'dry down' with hydrophobic treamtent additionally degrade during washing ('natural' down is fine),

Second this. I have a Cumulus X-lite 200. Comfort temp 4 degrees but honestly it can easily handle lower. For summer the one mentioned here above would be perfect.

Second this. I have a Cumulus X-lite 200. Comfort temp 4 degrees but honestly it can easily handle lower. For summer the one mentioned here above would be perfect.

super small and durable is a bit difficult, but I have a cumulus sleeping bag rated to 40f that weights 10oz and packs crazy small

For the sleeping bag I’d recommend a zpacks, timmermade or cumulus 30f range sleeping bag you could push into much colder temps wearing alpha 120 bottoms, down jacket, and down foot booties inside the sleeping bag. I’ve used this combo of clothing to push my 12oz 50f sleeping quilt down to 20f comfortably. If you plan to camp mostly in the summer I’d get the 50f bag and just wear more clothes inside it to push temps lower in fall. I switched to this technique and was able to reduce my pack size a lot and half the weight of my sleeping bag and its bulk. It works well since I’m already taking the alpha pants and down jacket anyways so I might as well wear them and save weight on the sleeping bag. The wind makes the biggest difference to me for how much insulation I need at night. For High Wind below freezing a windproof bivy that can fit over your pad and quilt makes a huge difference to your overall warmth and stoping drafts. Many UL quilts with 7D fabric are not very windproof and even a 20f bag can feel very cold at 20f in high winds. I like to summit camp and it’s often very windy above 6000ft. For the sleeping pad I’d recommend the thermarest nxt https://cascadedesigns.com/products/neoair-xlite-nxt-sleeping-pad?srsltid=AfmBOop1YJvl8n8oPU1vCNvveJ5sopEYhuUIcb1ORgJmz5-Sc-vxRd-W If 6.1 and the wide thermarest fits me but is still small. It packs down very small and is the most comfortable and insulated pad for the weight that I’ve tried yet. I have slept at 10f in the snow and been fine with it. You can also pair it with a gossamer gear thin light foam pad and gain more R values for freezing temps.

Cumulus x-lite is a great bag that is INSANELY packable. Worth the money, especially since you can customize a lot of options to fit your needs.

Take a look at cumulus bags. They can do custom fill (up or down, “waterproof” different fabrics etc ) and custom sizing for it as well if you wish. Not cheap but personally I think they’re the best down bags on the market.