I'd like to share my own personal experiences with kydex as a material for knifesheets. I bought a kydex sheet for Mora Frost knifes since these are the knifes I wear when I'm out in the woods, fishing, or anything that does not include EDC-carry, for which I wear a folder. It was from a a guy I got in touch with online and he had made some really cool holsters and sheets and I got this sheet and I thought I was gonna try it out and maybe get a holster for my pistol from his later on if the sheet was any good. First try was a late January ice-fishing trip with my son. Temps were down to -34.6 degrees Fahrenheit (Thank you Google). The sheet got really stiff at first, something that didn't surprise me much since alot of materials, including my toes and fingers, get stiff around these temperatures. Once I had used the knife and got it a bit wet before putting it back in the sheet it froze solid and when a bit of muscle was applied to get the knife out the sheet cracked lengthwise. I thought no more of it and went back to the plastic sheets that these knifes come with. While some people might say they are a bit "rattly" I after this experience see the point in this since it gives water the space to expand. This winter I tried a Kydex holster for my m/07 pistol while out on the ice for IPSC-training with the club. I had used the holster indoors quite a few times and it really worked well. When it was my turn I had been waiting for 40 minutes in -22 farenheit and I tried to draw but the pistol wouldn't move. Later on after a couple of minutes in room temperature it worked fine again. My personal conclusion is that kydex is pretty much useless if you use it in cold environments. After the knife experience I thought it was just a design-flaw, but I later realized it was probably the material in itself that just isn't cut out for cold weather. Leather rocks.