USG Durock Brand Fusion Primer is a one-coat, three-component, waterborne epoxy that has been specially formulated for interior applications as a consolidation primer for dusty compromised gypsum underlayments. This two-part kit will yield 5 gallons (17.9 L) of product. As a consolidation primer for compromised gypsum underlayments, USG Durock Fusion Primer reduces surface dust and chalkiness, and increases surface hardness and internal strength of the gypsum matrix to an acceptable level which then allows the application of USG Durock trowelable or USG Durock or USG Levelrock pourable products to repair the compromised gypsum underlayment surface. USG Durock Fusion Primer?s breathable characteristic also allows it to be applied onto either a wet, but set USG Levelrock Floor Underlayment, USG Durock Multi-Use Self-Leveling Underlayment, ora fully dried underlayment.