The knees are reinforced with a puncture-resistant 900d Cordura. Honestly, I thought the main breathable fabric wouldn’t hold up to hard-use, but so far they have proven to be durable. I even have friends who’ve used them hard over multiple seasons with no tears, rips or punctures to date. Banded makes an insulated version that’s warm enough for late-season diver hunts here in upstate New York, but I prefer the uninsulated models for season-long versatility. You can always wear layers of long underwear and wader pants on those single-digit days.