Supposedly a lifetime guarantee, but for the money if we have a yr or two outside of them we would be happy. Up to now, we like them much better than merino as our feet appear to stay drier. And so they appear to be Keeping up nicely. ✔️ Sturdiness: https://dog-dog-toys75072.affiliatblogger.com/84597149/everything-about-ninja-turtle-socks