The evacuation kit is very interesting. I purchased the size small as my dog wears the size small Front Range Harness. The size small just fits my guy, although I a medium might have been better and easier to get on him. I set up the harness at home so that it will be ready to use in case of emergency. I recommend doing this as there are quite a few straps to get sized to yourself and your pet. At first the set up looked difficult, but I was able to figure it out pretty quickly. Hopefully, I do not need to use the kit, but am glad that I will have it with me for mountain hiking.