Kevin 5 They’re actually Gore-Tex! But only the top half. The bottom half builds up a lot of condensation and can actually make your legs and feet wet from sweat, which happened to me a few times.There’s no option for larger or smaller sizes. I wear size 27 and 27.5 boots and these just barely fit. I doubt larger boots will be okay.The elastic cord is good too, but as I mentioned about the fit, it felt like I was about to break them every time I put them on. Thankfully replacements are quite cheap.