The Biopod Down Hybrid Ice Extreme makes no compromises when it comes to sleeping comfort. The fact that this is right at the top of the list of priorities is evident from the description: down-wool mixture for a more comfortable sleeping climate, heating element on the feet and a slightly wider cut for more freedom of movement. The numerous small details show that a lot of considerations went into the sleeping bag. Worth mentioning here are, for example, the straps with rubber nubs, which are attached to the back of the sleeping bag and limit slipping on the surface.

A sleeping bag serves to trap the heat radiated from the body and thus keep the environment around the body at a comfortable temperature. Especially in winter, cold feet often have trouble warming up the air around them. The integrated heating element supports this process by additionally warming the foot region. It is not intended as a permanent heater for the night, but can be switched off as soon as the sleeping bag is warm. Of course, this also saves electricity. The heating element heats up noticeably when you put your feet directly on it. However, this was not always the case for me because, as already mentioned, the sleeping bags are a bit larger than normal. So I didn't always feel the warm wires like heated socks. The heating element warmed up the area around the feet, which ultimately had the same effect: warm feet, a pleasant sleeping climate.

The wool added to the down not only regulates moisture, but also has a strong temperature-balancing effect. So I could sleep comfortably at -20°C as well as at 5°C.

I've developed a good deal of skepticism, especially when it comes to the temperature specifications for sleeping bags, and I often sleep with a bivy sack, thermal liner and possibly clothing. However, according to reports, the Down Hybrid Ice Extreme should keep you warm enough even below the -15°C intended for men ("limit"). That's why I lay down in my sleeping bag in Swedish Lapland on the Arctic Circle without a tent or other layers, just my underpants and a t-shirt on me. The thermometer dropped to -28°C during the night, but according to meteorological data and conversations with neighbors the next day, the temperature was more like -15 to -20 degrees. Towards morning it felt a bit chilly, but not enough to put on the sweater. It should also be mentioned that due to a misunderstanding with Grüezi Bag I assumed that the sleeping bag didn't have a warm collar, so I didn't even look for it, let alone pull it tight! Note: There is a thermal collar that nestles comfortably around the neck like a fur scarf. The drawstring can be stowed in a small side pocket, which is why I didn't notice it at first.

I like to roll over from my back to my side and back at night. Normally, cold gets into the sleeping bag through the side that is still compressed until it has puffed up again. This is not the case with the Down Hybrid Ice Extreme, probably due to the differently shaped chambers. This makes turning a lot more comfortable.

Another advantage of wool is that the sleeping bag bulges out very quickly. Pulled out of the pack sack, you can watch it puff up, it's practically ready to move into. But that brings me straight to the biggest (in the truest sense of the word) of the few disadvantages of this sleeping bag:
With a weight of approx. 1.5 kg, it is completely acceptable, even if it is a bit heavier than other models in this temperature class. However, the wool, which is not very compressible, makes for a huge pack size in my opinion! With the supplied compression bag and the straps stretched to the point of tearing, I get approx. ø28 x 29 cm, which corresponds to a volume of 18L, far from the 12.5L specified online (size 190 W). With another drybag I managed at least 16L, but the sleeping bag really can't be compressed much more with normal application of force. For me, who carries all my equipment including cooker, food, camera material and drone on my back, it is a real space eater. If you are traveling by car or, as is usually the case in Lapland, dragging your luggage behind you on a sled, then this is of course not a problem. On extreme and longer winter tours below -8 degrees, I will use the Down Hybrid Ice Extreme and look forward to a good night's sleep, but otherwise use a combination of 2 smaller sleeping bags, inlet, etc., which ultimately takes up less space.

What really bothers me about the sleeping bag - I originally wanted to list this later under "further comments" - is the inner pocket. It closes in the middle with a Velcro fastener. Smaller objects like earplugs or keys fall out. In practice, opening and especially closing the Velcro fastener proves to be extremely cumbersome, even after some practice. Since the two sides of the Velcro fastener tend to turn inside out, you have to use both hands and, ideally, be able to look. The opening faces down the side, which sometimes causes the power bank and smartphone to fall out before you can finish the "Velcro closure" project. Of course, this point of criticism has nothing at all to do with the actually important aspects such as (sleep) quality, and I can imagine that some readers have to smile... But this bag is annoying and I wish I had the little zipper of my old sleeping bag back.

Conclusion: In terms of sleep and where I sleep, I can still be quite a diva, despite spending so many nights outside. The Down Hybrid Ice Extreme opened my eyes to what is possible when it comes to sleeping comfort: "Like at home in your own bed" is the motto. I sleep a lot better in this sleeping bag than I am used to from my nights under the open sky. If it didn't fill what feels like half of my backpack, I would probably take it with me on all my adventures from autumn to spring as standard.

MORE NOTES ON SMALL DETAILS
The drawstring for the hood is elastic. When the temperatures are right, I make the opening very small and pull the cord properly. Sometimes I'm afraid that this drawstring will tear at some point. I would have preferred an inelastic and stronger drawstring that gave me direct feedback in the size of the hood opening. The drawstring then also presses on top of my nose, as I tend to slide upwards in my sleeping bag when I sleep. Since the cord clamp is attached close to the sleeping bag, I have to open it and either pull the cord through with the other hand or manually widen the sleeping bag opening. It would probably be a little easier if the cord clamp is not attached to the sleeping bag and can therefore be pulled to the end of the tightened cord with one hand movement.

Regarding the heating element: I think it's great that there is no built-in rechargeable battery, because (as Grüezi Bag assumed) I always have a power bank with me anyway. However, if the power bank and smartphone are in the same inner pocket on the left side as mentioned above, then the sleeping bag pulls a little to the left, which I notice in the centering of the opening. Possibly would have been a little more even with two pockets on both sides.

The heating element itself is well hidden. Curious as I was, I immediately looked for it and took it out. Only to realize that it's quite a hassle to put this back neatly into its designated pocket. I will probably always carry the heating element with me and only take it out for washing. The saved 50g are not really significant with a total weight of 1.5 kg.