Hadar's Clay™ One-fire Flex Clays are specialty clays suitable for using with embossing and cutting machines such as the Silhouette Cameo or Silhouette Curio. Unlike the Traditional/Flex clays, One-fire Flex Clays can be fired in only one phase. Hadar's Clay™ is metal clay in the form of powder. The powder is already mixed with a binder and all you have to do is add water.