Gunze's Mr. Epoxy Putty Pro-H hardens quickly even though it's high density, and is easy to sand. A strong ally of fans of modeling! The "H" in "Pro-H" indeed means "high density." Perfect for modeling and remodeling your models. A two-part epoxy putty that you knead together to "activate." Hardens in one to three hours. The 78 gram package includes 39 grams of putty and 39 grams of catalyst.