It's a stud. Made of rubber. Really. They work nearly as well as carbide studs, and dont' damage the pavement. Also, modern studless snows work better than studs almost all the time. The remaining exception is icy surfaces (not snowy) when the temperature is right around freezing. Colder than about 20 F, studs don't bite ice any better than rubber, and really cold, rubber wins. That's cars and light trucks, bikes are different, because the pressures are so different.