Down can only do its job if it can spread. This means that if it is compressed, for example by lying on it, it has almost no insulating effect. That’s why many ultralight hikers now swear by quilts.
The number of applications for such a ridiculously simple piece of fabric are very impressive. The purchase is worth it in any case. The Buff is basically nothing more than a tubular scarf which is made of various fabrics such as polyester, polyamide, merino, etc. together with spandex. Thus, it is extremely stretchy. Depending on the model, the Buff also offers UV50 protection. The colors and variations are very diverse.
Widely known, the cheap gasoline stove reached thanks to Andrew Skurka (Video: Andrew Skurka DIY stove). It was probably originally created by Jim Wood. It is a simple, lightweight and inexpensive alternative to gas stoves. I use it as a backup for longer hikes since I usually eat cold but am glad for a warm meal now and then.
For longer outdoor adventures you will need the Bear grylls axe, the Bear grylls knife and a strong paracord rope in case you have to abseil somewhere. In no case forget the folding shovel. The 4 KG extra weight is certainly well invested.