Monster Clay Standard Grade and Monster Clay Premium Grade Modeling Clays are sulfur free, medium firm, Professional Oil Based Clays. Both grades are composed entirely of non-toxic and organic components. The Standard Grade shares many of the same characteristics of the Premium Grade Modeling Clay but is tan in color, has a softer feel when warmed with increased elasticity and tack. Monster Clay Premium Grade has a drier, low tack feel, with a lower melt temperature. Monster Clay Premium will not stick to tools or fingers and is a mid tone brick red color.