Either silicone or nylon.
Silicone for Classic Black and Classic Blue, Nylon for Space Blue and Rainbow.
We are currently experiencing an issue where devices may not successfully pair with the Wyze app. Our team is aware and looking into it. Thank you for your patience while we work to get this resolved. Feel free to keep an eye out for updates https://support.wyze.com/hc/en-us/articles/360015979872-Service-Status-Known-Issues
Silicone for Classic Black and Classic Blue, Nylon for Space Blue and Rainbow.