skin–deep 
/ˈskɪnˈdi:p/ adjective
/ˈskɪnˈdi:p/ adjective : not very deep at all : relating to, affecting, or involving only the surface
▪ Beauty is only skin-deep. ▪ These reforms are more than skin-deep.
▪ Beauty is only skin-deep. ▪ These reforms are more than skin-deep.
